- 25.09.2019 at 16.00 in Blokhintsev Hall (BLTP, 4th floor)
**Lucia Oliva (GSI, Darmstadt & ITP, Goethe-Universit ̈at, Frankfurt am Main)**

*"Investigating relativistic proton-nucleus collisions and the influence of electromagnetic fields on final hadronic observables"*

Abstract:

The recent experimental observations of azimuthally anisotropic flow in small systems at RHIC and LHC energies has stimulated new interest in these collisions, traditionally regarded only as control measurements for heavy-ion collisions and now becoming a new area of study for the formation and evolution of quark-gluon plasma. In the early stage of proton-nucleus collisions extremely intense electromagnetic fields are produced; respect to heavy-ion collisions, in these asymmetric systems the electric field generated along the impact parameter axis is very high and comparable to the magnetic field perpendicular to the reaction plane. Furthermore, particle rapidity densities are strongly asymmetric inside the overlap area due to the different number of nucleons in the colliding nuclei. One of the main effects of this combined asymmetry of electromagnetic fields and particle distributions is a splitting in the directed flow of positively and negatively charged mesons in the nucleus-going side. By means of microscopic calculations within the Parton-Hadron-String Dynamics (PHSD) approach we study the main features and final hadronic observables of p+Au reaction at top RHIC energy, investigating in particular the influence of the electromagnetic fields on flow anisotropies.

- 31.07.2019
__Vladimir Voronin__(BLTP), Sergei Nedelko (BLTP)

*"Finite size effects for QCD effective potential"*

Abstract:

Finite size effects for QCD effective potential of Abelian (anti-)self-dual gluon field are studied. The effective potential is calculated within the framework of zeta function regularization for spherical four-dimensional domain of radius R in Euclidean four-dimensional space-time. It is shown that gluon and quark quasi-zero modes play important role in the dependence of the effective potential both on the background field strength and the domain size. The infinite-size strong-field limit of the effective potential, that is determined by the asymptotic freedom, requires treatment of the quasi-zero modes beyond one-loop approximation. It is shown that under certain conditions global minimum of the effective potential exists at finite nonzero values of both background field strength and domain size $R$. Existence of such a minimum would strongly support the mean field description of QCD vacuum in terms of statistical ensemble of almost everywhere homogeneous (anti-)self-dual Abelian gluon fields. As has been shown earlier, such a description of QCD vacuum demonstrates highly promising features for studying confinement, chiral symmetry realization and hadronization in QCD. - 24.07.2019
**K.A. Bugaev (BITP, Kiev)**

*"Recent signals of two QCD phase transitions in heavy ion collisions in the NICA-FAIR energy range of collisions"*pdf

Abstract:

During last few years two groups based on many irregularities and possible signals independently suggested that the 1-st order phase transition of chiral symmetry restoration in hadronic phase may occur in the central nuclear collisions at the center-of-mass energies 3.8–4.9 GeV, while a weaker deconfinement phase transition of 2-nd order may be reached at the center-of-mass collision energies 9-10 GeV. Later on the third group studying the fluctuations of light nuclei concluded that the center-of-mass collision energy 8.8 GeV may be the nearest vicinity of the critical endpoint of QCD matter phase diagram. Hence in this talk I will present the most striking signals of two QCD phase transitions which are deduced from the existing experimental data. Based on a recent analysis of the data description quality factor of 10 existing event generators of nucleus-nucleus collisions in the range of center of mass collision energies from 2.1 GeV to 17.3 GeV I will present the arguments which provide an independent evidence that two QCD phase transitions occur at the center-of-mass energies 3.8–4.9 GeV and 9-11 GeV. The prospects for detecting these phase transitions at NICA-FAIR energy range will be discussed as well. - 06.06.2019
**Yuri Sinyukov (BITP, Kiev)**

*"Space-time picture and bulk observables in relativistic heavy ion collisions"*pdf

Abstract:

We analyze the experimental data in nucleus-nucleus collisions at the RHIC and LHC, such as the particle number ratios, hadron&photon spectra and their anisotropy coefficients v_n, also femtoscopy correlations, within the full evolutionary model . The latter includes formation of the initial state and initial conditions in relativistic heavy ion collisions, a gradual (partial) thermalization of the matter created, subsequent viscous hydrodynamic relativistic expansion of quark-gluon plasma, hadronization process, particlization of the hadron matter and, finally, scattering of secondary particles and spectra formation. Within such an integrated HydroKinetic Model (iHKM) we predict some effects and present the physical interpretation of the results. - 29.05.2019
**Maria Paola Lombardo (INFN Sezione di Firenze)**

*"Topology of strong interactions, between the QCD and the EW transition. "*pdf

Abstract:

Strong interactions' topology is a rich theoretical subject with phenomenological implications: at low temperature topology holds the key to a complete understanding of the hadron spectrum; around the QCD transition the interplay of topology, axial and chiral symmetries affects the nature of the hot medium and possibly its experimental signatures; for even higher temperatures, topology determines the density of the QCD axions, which are candidate dark matter particles. The talk will focus on results for the topological charge, its susceptibility and its correlator in the QCD plasma, and on their implications on the aspects outlined above. - 2.04.2019
**Anastasia Golubtsova (BLTP)**

*"Lectures on Holography for QCD. Lecture 2."*

Abstract:

In this lecture we will focus on the AdS/CFT correspondence for the thermal case. We will discuss the holographic dictionary and applications of the AdS/CFT duality to equilibrium physics. Namely,

-Types of 5d black holes.

-Black hole thermodynamics and free energy of the dual theory.

-The Hawking-Page phase transition as the holographic encoding of confinement/deconfinement.

-Holographic dictionary for QGP.

- 21.02.2019
__M. Bordag__(Universität Leipzig, Germany) and V. Skalozub (Dnipro National University, Ukraine)

*"Scattering of photons on $A_0$-background in a quark-gluon plasma"*

Abstract:

In heavy ion collisions a quark-gluon plasma is supposed to be created whose temperature is in the deconfinement region allowing for a quasiparticle description. Within this description condensate fields may exist. We focus on a spontaneously generated $A_0$-background, which is equivalent to an imaginary chemical potential. The corresponding symmetry breaking invalidates the Furry theorem and allows for non-vanishing tadpole and triangle diagrams. First we consider a tadpole diagram (closed quark line). It can be easily re-summed and results in a redefinition of $A_0$. Next, we consider a triangle diagram with two external photon lines and a quark current in the third vertex. We discuss the resulting scattering of photons. - 13.02.2019
**Anastasia Golubtsova (BLTP)**

*"Lectures on Holography for QCD. Lecture 1. Overview of the AdS/CFT correspondence"*

Abstract:

-Motivation from QCD

-Symmetries of AdS and CFT

-Holographic vocabulary

-Temperature and black holes

-Free energy and renormalization

-Chemical potential

- 23.01.2019
**Anastasia Golubtsova (BLTP)**

*"More on holographic duals for QCD, towards finite chemical potential"*pdf

Abstract:

In this talk we will discuss of the solvable holographic model for QCD presented in arXiv:1803.06764. We will consider in the detailed form the holographic dual governed by the two exponential dilaton potential. The solutions to this model can be interpreted as RG flows interpolating between different fixed points including those corresponding to AdS boundaries. The generalization to the non-zero temperature case will be presented. We will also illuminate possible ways of introducing finite chemical potential via holographic duality. - 26.12.2018
**V.I. Zakharov (ITEP, Moscow)**

*"Imaginary Acceleration (based on arXiv:1807.03584 [hep-th])"*pdf

Abstract:

N/A - 25.12.2018
**A.B. Larionov (Institut für Kernphysik, Forschungszentrum Jülich, Jülich & FIAS, Frankfurt am Main & NRC "Kurchatov Institute", Moscow)**

*"Nucleus- and particle-nucleus collisions in the Giessen Boltzmann-Uehling-Uhlenbeck model (GiBUU)"*pdf

Abstract:

Microscopic transport approach can be applied to a broad range of inclusive nuclear reactions, where the quantum states of the outgoing nuclear systems are not resolved. The latter condition facilitates the use of single-particle distribution functions, i.e. Wigner functions in 6-dimensional phase space. In the semiclassical approximation, the time evolution of a Wigner function for the system of fermions is described by the Boltzmann-Uehling-Uhlenbeck equation which includes the mean field potential and collision term with Pauli blocking factors. The most powerful method to solve this equation is based on the test particle method and the Monte-Carlo simulation of the collision term. Based on this method, large number of numerical models have being developed. GiBUU is one of the most elaborated microscopic hadronic transport models. The basic features of the GiBUU model will be presented. The applications of the model to heavy-ion collisions at the beam energies of 1-40 A GeV, to antiproton- and photon-nucleus reactions will be discussed. - 25.12.2018
**Igor N. Mishustin (NRC Kurchatov Institute, Moscow and FIAS, Frankfurt)**

*"Phase transitions in hot nuclear matter composed of nucleons and alpha-particles"*pdf

Abstract:

The finite-temperature equation of state of chemically-equilibrated mixture of alpha particles and nucleons is studied in the mean-field approximation. We use Skyrme-like parametrization of the mean-field potentials as functions of partial particle densities, which contain both attractive and repulsive terms. The phase diagram of the alpha-nucleon mixture is studied with a special attention to possible phase transitions. We have found two first-order phase transitions of liquid-gas type, stable and metastable, which differ significantly by the fractions of alpha particles. It is shown that alpha particles can also form a Bose condensate, but this state is metastable. - 05.12.2018
__Natalia Kolomoyets__, Vladimir Skalozub (Dnipro National University, Ukraine)

*"Screening mass of gluons in presence of external Abelian chromomagnetic field"*pdf

Abstract:

Screening mass is the main macroscopic characteristic of a gauge field at finite temperature. It shows how fast the gauge field decreases in space. There are electric and magnetic screening masses. It is known that in SU(N) gauge theory the former one is proportional to $gT$, while the second one is proportional to $g^2T$. So, at high temperature the magnetic mass is much less than electric one, and is harder to investigate. In the current research the contribution of various color components of chromomagnetic field into the magnetic mass is investigated by methods of lattice gluodynamics at finite temperature. The interaction between a monopole-antimonopole string and external neutral Abelian chromomagnetic field is considered. The string is introduced in the standard way described by Srednicki and Susskind. The neutral Abelian field is introduced in the form of a flux through the twisted boundary conditions. Monte Carlo simulations are performed on 4D lattices. The derivative of the free energy with respect to the inverce coupling is the measured quantity. In SU(2) case in the absence of the external Abelian flux, the result by DeGrand and Toussaint is reproduced. We have obtained that the flux addition weakens the screening of the string field. The contribution of the neutral Abelian flux to the measured quantity has the enhancing factor form. This behavior independently confirms the long-range nature of the neutral Abelian field reported in the literature. In SU(3) case even without the additional Abelian flux the absence of screening of the monopole-antimonopole string has been obtained. This result is unexpected and is discussed within the context of the results of other investigations. - 04.12.2018
**Dragos-Victor Anghel (Horia Hulubei National Institute of Physics and Nuclear Engineering, Romania)**

*"Physics at the meso-scale: toroidal moments and non-extensive entropies"*pdf

Abstract:

1. Statistical processes of mesoscopic systems (e.g. nano-, nuclear, and astronomic systems) cannot be described, in general, by the Boltzmann-Gibbs entropy (mainly) because they are not extensive. In such cases, other types of entropies—the so called non-extensive entropies—seem to be better suited for the task. There are different techniques for calculating the equilibrium probability distributions of non-extensive systems, techniques which may not lead to the same results. The justification of these techniques come, eventually, a-posteriori, by comparing the calculated distributions with the ones measured or inferred from the experiment. In this presentation we propose a general approach for calculating the equilibrium probability distributions, applicable to both, extensive and non-extensive systems, and to any expression of the entropy. We exemplify the procedure by applying it to Boltzmann-Gibbs, Renyi, Tsallis, and Landsberg-Vedral entropies and discuss the results (D. V. Anghel and A. S. Parvan, J. Phys. A: Math Theor. 51, 446002, 2018). 2. Although the multipole decomposition of charge and current densities is almost as old as classical electrodynamics, a whole class of terms has remained unknown for a long time. The history of toroidal moments began with Zeldovich's pioneering work (Zh. Exp. Teor. Fiz. 33, 1531, 1957; Sov. Phys. JETP 6, 1184, 1958). He was the first to note that a closed toroidal current (which cannot be reduced to a usual charge or magnetic multipole moment) represents a certain new kind of dipole. The necessity for studying the toroidal momentum operator is justified by its large area of applicability in physics at any scale (subnuclear, nuclear, atomic, molecular and condensed matter physics). There is a whole class of particles--the Majorana fermions and self-conjugate bosons--which are not allowed to possess any electromagnetic structure other than toroidal multipole moments and this comes from CPT invariance alone. Meanwhile, the most important facts we need to know about an operator are its spectrum and its eigenfunctions. Consequently, in this presentation we shall solve this problem. In order to do this, we introduce the toroidal momentum operator and study some of its properties. We propose a new set of coordinates in which the operator becomes a simple derivative along one of the coordinates. This enables us to find the eigenvalues and the eigenfunctions (D. V. Anghel, J. Phys. A: Math. Gen. 30, 3515, 1997). - 31.10.2018
**Roman Zhokhov (IHEP, Protvino), Tamaz Khunjua (Moscow State University)**

*"Phase diagram and dualities of dense baryonic matter with chiral imbalance"*pdf, pdf

Abstract:

In this talk the phase structure of the dense quark matter has been investigated in the presence of baryon μ_B , isospin μ_I , chiral μ_5 and chiral isospin μ_I5 chemical potentials in the framework of Nambu--Jona-Lasinio model with two quark flavors. It has been shown that in the large-N_c limit ( N_c is the number of colors of quarks) there exist duality correspondences at the phase portrait. The first one is a duality between the chiral symmetry breaking and the charged pion condensation phenomena. And there are two other dualities that hold only for chiral symmetry breaking and charged pion condensation phenomena separately. For example, we have shown that charged pion condensation does not feel the difference between chiral and isospin imbalances of the medium. The duality between the chiral symmetry breaking and the charged pion condensation phases has been established for the first time in low-dimensional toy model for QCD then it has been checked to take place in a more realistic effective model for QCD. One of the key conclusions of our studies is the fact that chiral imbalance generates charged pion condensation in dense baryonic/quark matter. It was also shown that our results in particular cases are consistent with the simulation of lattice QCD, which is possible for isospin and chiral chemical potentials. Moreover, in a number of works, catalysis of chiral symmetry breaking by chiral imbalance was predicted, but there were also works that predict the opposite effect. After lattice calculations that confirmed the effect of catalysis of chiral symmetry breaking, we can, of course, say that the problem has been solved, but it would be interesting to find out the reasons for the discrepancy between the results of effective models. We have made a small step in this direction and showed that, based on the dualities and the well-studied properties of the phase structure of QCD with only isotopic imbalance, one can conclude that there should be an effect of catalysis of chiral symmetry breaking. It was also shown that the fact that the chiral imbalance generates the phenomenon of charged pion condensation in dense baryonic/quark matter also remains true for the case of charge neutral matter, which is interesting in the context of the astrophysics of neutron stars. It is known that chiral imbalance can occur in high energy experiments on the collision of heavy ions, due to temperature and sphaleron transitions. Our studies show that different types of chiral imbalance can occur in the cores of neutron stars or in heavy ion experiments where large baryon densities can be reached, due to another phenomenon - the so-called chiral separation effect (although there were references to this possibility, we explored it in more details). - 25.10.2018
**Tobias Fischer (Institute of Theoretical Phyiscs, University of Wroclaw, Poland)**

*"Explosions of massive blue-supergiant stars triggered by the QCD phase transition "*pdf

Abstract:

Motivated from the observations of yet-unexplained explosive phenomena associated with massive blue-supergiant stars with zero-age main sequence (ZAMS) masses around 50 M_o, new light has been shed on the old idea [1] that the appearance of QCD degrees of freedom may explain such cosmic events [2]. Obeying chiral physics and taking yet-another important observation of the very existence of massive neutron stars of 2 M_o seriously into account, puts sever constraints on the behavior of the equation of state at supersaturation density (\rho_{sat}). In particular, sufficient stiffness with increasing density is required. Both aspects indicate rather high densities for the hadron-quark phase transition in excess of 2\rho_{sat} (at zero temperature). As a consequence, this excludes low- and intermediate mass stars (~ 10 − 15 M_o ) -- they are canonically considered in supernova studies -- from the presence of ’exotic’ high-density phases. On the other hand, during the evolution of very massive core-collapse supernova progenitors with ZAMS masses of about 50 M_o , significantly higher core temperatures and densities are reached, where the appearance of the hadron-quark phase transition triggers not only the supernova explosion onset but also a millisecond neutrino burst is released. The latter observable signal provides evidence not only for the presence of a 1st-order phase transition at supersaturation density but contains also details about its properties. The future observation of such a feature from the next galactic event will allow us to either confirm such scenario or, if not observed, rule out a (strong) 1st-order phase transition at high densities encountered in astrophysics. In this talk I will review this scenario in the light of presently known constraints from nuclear physics as well as observations. The latter includes the first binary neutron star merger event associated with GW170817 [3]. Furthermore, I will discuss implications for astrophysics, e.g., the remnants from such supernova explosions are massive neutron stars with quark-matter core of 2 M_o at birth.

Keywords: core-collapse supernovae --- equation of state --- quark matter

References:

[1] I. Sagert, T. Fischer, M. Hempel, G. Pagliara, J. Schaffner-Bielich, et al., ``Signals of the QCD phase transition in core-collapse supernovae,'' Phys.Rev.Lett., 102, 081101 (2009).

[2] T. Fischer, N.-U. F. Bastian, M.-R. Wu, P. Baklanov, E. Sorokina, S. Blinnikov, S. Typel, T. Kl¨ahn, and D. B. Blaschke, ``Quark deconfinement as supernova explosion engine for massive blue-supergiant stars,'' Nature Astronomy (in press), ArXiv e-prints astroph.HE/1712.08788 (2017).

[3] B. P. Abbot, \textit{et al.} [LIGO scientific and Virgo collaborations] ``GW170817: ``Observation of Gravitational Waves from a Binary Neutron Star Inspiral'', Phys.Rev.Lett., 119, 161101 (2017) - 26.09.2018
**Giuseppe Policastro (Ecole Normale Superieure, Paris)**

*"On some solvable non-conformal holographic models for QCD "*pdf

Abstract:

In recent years the holographic correspondence has been shown to be a very useful tool to get theoretical insight into strongly coupled systems such as the QCD quark/gluon plasma and strongly correlated electrons among others. I will present a class of holographic models that are useful toy models, because they can be studied analytically while having features resembling the real QCD, in particular for the running of the coupling. I will discuss the black hole solutions in these models that are dual to the plasma, and their unusual thermodynamic and transport properties as seen in the collective modes spectrum. - 03.09.2018
**David Fuseau (SUBATECH, Nantes)**

*"Equation of state at finite temperature and finite chemical potential using PNJL model "*pdf

Abstract:

We present an equation of state at finite temperature and finite chemical potential using the PNJL model. The equation of state goes to the next to leading order O(1/N_c) including mesons contributing to the pressure of the medium below T_c. Together with a new parametrisation of the effective Polyakov loop involving the presence of quarks in the determination of the critical temperature, we determine pressure at zero chemical potential matching the result of the lattice and expand to finite chemical potential. Also derivatives such as the entropy density, energy density, measured interaction and speed of sound are very similar to lattice results at zero chemical potential and can be expanded to finite chemical potential. Regarding the finite chemical potential, the Taylor expansion around zero chemical potential also matches the results of the lattice. Main applications could be neutron star calculations and input for transport hadronisation. - 09.07.2018
**Trambak Bhattacharyya (BLTP JINR & University of Cape Town)**

*"Non-extensive Statistics in High Energy Physics"*pdf

Abstract:

We shall discuss the basics of the Tsallis Non-extensive distribution and afterwards, we discuss the analytical calculations of the Tsallis thermodynamic quantities and applications of the Tsallis statistics in multi-particle production and in characterizing the hot and dense medium (Quark Gluon Plasma) created in high energy collisions. - 04.07.2018
**S. Khlebtsov,**__Y. Klopot__(BLTP JINR), A. Oganesian, O. Teryaev

*"Dispersive approach to non-Abelian axial anomaly and $\eta$, $\eta'$ production in heavy ion collisions."*pdf

Abstract:

We sudy manifestations of strong and electromagnetic axial anomalies in two-photon decays of $\eta$ and $\eta'$ mesons. Applying dispersive approach to axial anomaly in the singlet current, we obtain an anomaly sum rule containing strong and electromagnetic anomaly contributions. The relevant low energy theorem was generalized to the case of mixed states and used to evaluate the subtraction constant of the strong anomaly-related form factor. We made a numerical estimation of the contributions of gluon and electromagnetic anomalies to the two-photon decays of $\eta$ and $\eta'$ mesons and found significant suppression of the gluon anomaly contribution. We duiscuss the rate of direct production of $\eta$ and $\eta'$ mesons in heavy ion collisions. - 04.04.2018
__G. Prokhorov__(BLTP JINR), O. Teryaev

*"Anomalous axial current from covariant Wigner function and thermodynamic equilibrium density operator"*pdf

Abstract:

We considered a rotating and accelerated moving medium consisting of weakly interacting fermions in a state of local thermodynamic equilibrium based on two different approaches. In the first of the approaches, the properties of such a medium are described using the covariant Wigner function. We derived a formula for the axial current outside the perturbation theory, leading to a Chiral vortical effect in the limiting case. It is shown that in the limit of massless fermions the terms of higher orders in the thermal vorticity tensor are mutually compensated. In order to verify the results obtained, a second approach to the calculation of the axial current was used, based on the quantum density functional for a medium with rotation and acceleration. Carrying out the calculation of thermodynamic averages in the framework of quantum field theory at finite temperatures in the third order of perturbation theory, we obtained the mean values of the axial and vector currents. A generalization is made to the case of a nonzero axial chemical potential. The results obtained with the help of the Wigner function and the density operator are compared with each other and with the consequences of other approaches, such as effective field theory with axial anomalies. Based on the obtained formulas for the axial current, the correspondence of various approaches to the calculation of polarization of baryons is justified. - 14.03.2018
__M.I. Krivoruchenko__(ITEP & BLTP JINR), D.K. Nadyozhin, A.V. Yudin

*"Hydrostatic equilibrium of stars without local electroneutrality"*pdf

*"Гидростатическое равновесие звезд в отсутствие локальной электронейтральности"*

Abstract:

В нерелятивистской теории гравитации найдено общее решение уравнений гидростатического равновесия двухкомпонентного вещества, состоящего из ионов одного сорта и электронов, в отсутствие локальной электронейтральности. Система уравнений гидростатического равновесия принадлежит семейству сингулярно возмущенных систем обыкновенных дифференциальных уравнений. В согласии с теоремой Пуанкаре о разложении и критерием неаналитичности, известным как «аргумент Дайсона», общее решение имеет существенную особенность по гравитационной константе G в точке G = 0. Регулярная часть решения определяется, исходя из локально нейтрального решения в виде степенного ряда по G. Во внутренних слоях звезды нерегулярная часть решения мала, она может быть найдена с помощью асимптотического метода ВКБ, хорошо известного в квантовой механике. Вблизи поверхности звезды регулярная и нерегулярная компоненты сравнимы, они определяют свойства электронной или ионной оболочки. При фиксированных массе и радиусе заряд звезды изменяется в пределах от -0.1 до 150 Кл. Параметры оболочки экспоненциально чувствительны к вариациям плотности заряда в центре звезды. Представлены точные общие решения двух моделей звезд, не предполагающие локальной электронейтральности вещества.

https://arxiv.org/abs/1802.10082 - 07.03.2018
**Ya. Shnir (BLTP)**

*"Rational maps, crystals and multisolitons in the Skyrme model"*pdf

Abstract:

Relation between Yang-Mills theory and Skyrme model is discussed. We consider rational map approach and the structure of multisoliton solutions of the Skyrme model and the Faddeev-Skyrme model. The properties of triply periodic Skyrme crystals in the generalized Skyrme model are investigated. Various scenarios of phase transitions from the low-density phase to the high-density phase are examined for different choices of the parameters of the model. Considering the near-Bogomolny-Prasad-Sommerfeld submodel, we found that there are indications of the phase transition from a low-density quasi-liquid phase to the high-density symmetric phase of the Skyrmionic matter. - 27.02.2018
**Andrey Kotov (BLTP JINR & ITEP NRS KI)**

*"Study of properties of two color QCD at nonzero baryon density by means of lattice simulation"*pdf

Abstract:

Vacuum and finite temperature properties of QCD are well studied due to the method of lattice simulations. Unfortunately, in general case lattice simulations cannot be applied for QCD at nonzero baryon density due to the sign problem. In this report we present the results of lattice simulation of the theory which is free from the sign problem - two color(SU(2)) QCD at nonzero baryon density. Both SU(3) and SU(2) theories have many common phenomena and properties and study of SU(2) QCD can provide some information about the properties of real QCD. Calculations were carried out at zero temperature and with two flavors of dynamic quarks. In our study we found several phases of dense two color QCD: the hadronic phase at small chemical potential (\mu_q); the phase of Bose-Einstein condensation of scalar diquarks at intermediate values of \mu_q; the phase with condensation of quark Cooper pairs at large \mu_q. At ultrahigh densities (\mu_q~1000 MeV) we found confinement/deconfinement transition which manifests itself in rising of the Polyakov loop and vanishing of the string tension. Properties of the deconfinement phase at large densities are similar to weakly interacting gas of quarks and gluons, contrary to Quark-Gluon Plasma at large temperatures and zero baryon density. - 21.02.2018
**O.E. Solovjeva (ITEP)**

*"Hadrons in a strong magnetic field on the lattice" (in Russian)*pdf

*"Адроны в сильном магнитном поле на решётке"*

Abstract:

Доклад будет посвящён результатам исследования магнитных характеристик мезонов и предварительным результатам в случае нейтрона методами решёточной калибровочной теории. Вычисляются магнитная дипольная поляризуемость, магнитная гиперполяризуемость и магнитный момент, которые для большинства мезонов на настоящий момент не были найдены экспериментально. Для остальных мезонов между теоретическими предсказаниями различных феноменологических моделей и экспериментально полученными данными в настоящее время наблюдаются существенные расхождения. Полученные методами решёточной калибровочной теории значения магнитной поляризуемости заряженного пи-мезона согласуются с предсказаниями киральной теории возмущений и экспериментально полученным значением. - 14.02.2018
**Felix Ziegler (Institute for Theoretical Physics, Heidelberg University)**

*"Novel lattice simulations for transport coefficients in gauge theories"*pdf

Abstract:

Transport coefficients, such as the temperature-dependent shear and bulk viscosities, are essential QCD ingredients in the hydrodynamical description of relativistic heavy-ion collisions. The extraction of the transport coefficients from lattice simulations is extremely challenging since a reliable spectral reconstruction from Euclidean data at low frequencies is required. In standard simulations at finite temperature this reconstruction is based on the discrete Matsubara frequencies, and is exponentially hard: the thermal part of the low frequency information is hidden in the thermal decay of the Euclidean data at large frequencies. In order to overcome this limitation, we apply the novel approach for thermal fields on the lattice [1] to gauge fields [2]. The formalism operates in a non-compact imaginary time domain that leads to continuous imaginary time frequencies. The quantum evolution is formulated as an initial value problem and the thermal initial conditions are supplied by a standard lattice simulation. We present results for the energy momentum tensor correlation function in SU(2) Yang-Mills theory in the confined and deconfined phase. Convergence properties to the standard results at finite Matsubara frequencies are discussed. Moreover we show first results for the corresponding spectral functions obtained via the Bayesian BR method [3]. We assess the viability of the method applied to gauge fields and its ability to provide a robust estimate for transport coefficients.

[1] J.M. Pawlowski, A. Rothkopf, arXiv:1610.09531 [hep-lat]

[2] J.M. Pawlowski, A. Rothkopf and F. Ziegler (in progress)

[3] Y.Burnier, A.Rothkopf, PRL 111, 182003 (2013) - 06.12.2017
**V.V. Goloviznin,**__A.M. Snigirev__(SINP MSU & BLTP JINR), G.M. Zinovjev.

*"Anisotropy of thermal photons and dileptons"*pdf

Abstract:

Search for the signals of a new state of matter, quark-gluon plasma (QGP), is one of the main goals of experiments on heavy-ion collisions at high energies at modern colliders RHIC and LHC and at coming soon facilities FAIR and NICA. In this talk the meaningful specific anisotropy in the angle distribution of leptons with respect to the three-momentum of pair is predicted as a feasibility signature of synchrotron-like mechanism resulting from the quarks interacting with a collective confining color field in the heavy ion collisions. The photon and lepton pair production rate and the spectrum of pair invariant mass are presented for this new dilepton source that is apparently not taken into consideration in the available phenomenological estimates. - 25.10.2017
**Maksim Ulybyshev (Regensburg U.)**

*"Topologically protected states in 2D and 3D: spin-momentum and valley-momentum locking mechanisms."*pdf

Abstract:

Topological insulator is a special state of matter which has a gap in the bulk, but hosts gapless surface modes protected by non-tirivial topological invariant. Spin-momentum and valley-momentum locking mechanisms (the former one caused by strong spin-orbital coupling) are the underlying physical reasons for the appearance of the non-trivial topology of the surface modes. Topological protection suppresses the backscattering for electronic states on the surface thus leading to promising potential applications in "dissipationless" electronic and spintronic devices. We will review the basic concepts in the field and the most prominent lattice models hosting the topologically protected modes. Namely, we will describe the Kane-Mele model on hexagonal lattice in two dimensions and some lattice models on square and diamond lattices in three dimensions. We will also describe the possibilities for artificial engineering of topological insulators with both spin- and valley-momentum locking mechanisms using the deposition of adatoms in top of graphene sheet.

The stability of topological insulator against the effects of disorder and electron-electron interaction will be discussed. Some connections to Lattice QCD will be also reviewed. For instance, the prominent Wilson fermions in some region of parameters mimic the presence of spin-orbital coupling and can be used as a model for 3D topological insulator. - 18.10.2017
**E.-M. Ilgenfritz (BLTP JINR) (with J.M. Pawlowski, A. Rothkopf (Heidelberg) and A.M. Trunin)**

*"Transversal and longitudinal gluon spectral functions across the phase transition from twisted mass lattice QCD with N_f=2+1+1 flavors"*pdf

Abstract:

I report on the first application of a novel, generalized Bayesian reconstruction (BR) method for spectral functions to the characterization of QCD constituents. These spectral functions find applications in off-shell kinetics of the quark-gluon plasma and in calculations of transport coefficients. The new BR method is applied to Euclidean propagator data, obtained in Landau gauge on lattices with $N_f=2+1+1$ dynamical flavors by the ``twisted mass at finite temperature'' (tmfT) collaboration. The deployed reconstruction method is designed for spectral functions that can exhibit positivity violation (opposed to that of hadronic bound states). The transversal and longitudinal gluon spectral functions show a robust structure composed of quasiparticle peak and a negative trough. Characteristic differences between the hadronic and the plasma phase and between the two channels become visible. We obtain the temperature dependence of the transversal and longitudinal gluon masses. - 14.06.2017
**M. I. Krivoruchenko (ITEP, Moscow & BLTP JINR & MIPT, Dolgoprudny)**

*"Equation of State of Neutron Matter in the Model of Composite Quark Bag "*pdf pptx

"Уравнение состояния нейтронной материи в модели Составного кваркового мешка"

Abstract:

Согласно Дайсону (1957 г.) полюса Кастильехо, Далица и Дайсона (КДД) обусловлены существованием связанных состояний и резонансов. Обсуждается новый тип КДД полюсов, связанный с существованием примитивов Джаффе и Лоу, т. е. полюсов P матрицы или, эквивалентно, соответствующих им нулей D функции на унитарном разрезе. Уравнение рассеяния Лоу обобщается на амплитуды, допускающие КДД полюса нового типа. Связь между КДД полюсами и примитивами иллюстрируется на примере описания в модели Составного кваркового мешка (СКМ) амплитуд NN рассеяния в S- и Р- волнах с учетом аналитичности и унитарности [1]. Фазовый анализ, таким образом, указывает на существование 6-и кварковых примитивов в каналах 3S1, 1S0 и 3P0. Сигнатура примитива – нулевая фаза рассеяния с отрицательным наклоном. В зависимости от характера взаимодействия с континуумом компаунд состояния проявляют себя в виде связанных состояний, резонансов, или примитивов. Если взаимодействие испытывает возмущение, компаунд состояние может изменить свои свойства. В моделях s-канального обмена электромагнитные взаимодействия, вообще говоря, сдвигают примитивы с унитарного разреза, превращая их в узкие резонансы. Дана оценка этого эффекта в рр канале 1S0. Электромагнитные взаимодействия трансформируют примитив с массой 2000 МэВ в дибарионный резонанс примерно той же массы и шириной 260 кэВ [2]. В модели СКМ, где NN взаимодействие описывается в терминах s-канального обмена 6-и кварковыми примитивами, построено уравнение состояния нейтронной материи при плотности ниже 0.5/фм^3. Зависимость энергетической щели сверхпроводящей фазы нейтронной материи от плотности количественно согласуется с предсказаниями моделей однобозонного обмена [3].

[1] M. I. Krivoruchenko, Phys. Rev. C 82, 018201 (2010).

[2] M. I. Krivoruchenko, Phys. Rev. C 84, 015206 (2011).

[3] М. И. Криворученко, Письма в ЭЧАЯ (2016), в печати. - 16.02.2017
**A. M. Snigirev (Skobeltsyn Institute of Nuclear Physics, Moscow)**

*"Multiparton Interactions in Quantum Chromodynamics"(in Russian)*pdf

*"Многопартонные взаимодействия в квантовой хромодиамике"*

Abstract:

Будет дан обзор результатов, полученных в недавние годы в решении фундаментальной научной проблемы о проверке теории сильных взаимодействий (КХД) в режиме свервысоких плотностей энергии и температур. В этом режиме значительно возрастает роль жестких многопартонных взаимодействий, которые являются важным и значимым фоном при поиске сигналов новой физики на Большом адронном коллайдере (БАК).

Для моделирования двукратных партонных рассеяний необходимо знать двухпартонные функции распределения как решеня соотвествующих уравнений (обобщение уравнений ДГЛАП). Из этих уравнений следует, что факторизационная гипотеза, часто применяемая для двухпартонных функций распределения при анализе экспериментальных данных по двойным партонным рассеяниям, явно противоречит уравнениям эволюции КХД и может быть использована только как первое приближение в ограниченном интервале изменения масштаба жесткости процесса. С увеличением этого масштаба вклад возникающих динамических КХД корреляций в двухпартонные функции распределения возрастает по сравнению с факторизационной компонентой и может быть экспериментально обнаружен.

Проведенные Коллаборацией D0 в 2010 году на Тэватроне измерения эффективного сечения двойных партонных рассеяний интерпретируются именно как первое указание на эволюцию двойных партонных распределений, которая имеет такой же статус достоверности в КХД, как и уже подтвержденная экспериментально эволюция одиночных распределений. - 30.11.2016
**Victor Braguta (IHEP, Protvino & ITEP, Moscow & Far Eastern Natl. U., Vladivostok & MIPT, Moscow)**

*"Study of temperature dependence of QCD viscosity"*pdf

Abstract:

We have studied the QCD viscosity in the vicinity of confinement/deconfinement transition in lattice simulations. In particular, we have computed with high accuracy the correlators of energy-momentum tensor in gluodynamics in the temperature range T/Tc=(0.9, 1.5). Using these correlation functions, we evaluated the spectral densty. Using it, we finally calculated the viscosity. The results of the calculation are in agreement with the values of viscosity, obtained in the RHIC experiment. - 23.11.2016
**S.P. Khlebtsov (ITEP, Moscow)**

*"Analysis of the e+e- ->pi^0 gamma process using anomaly sum rules approach "*pdf

Abstract:

The process $e+e- -> gamma* -> pi^0 gamma$ was considered using time-like pion transition form factor, obtained in the approach of the Anomaly Sum Rules(ASR). The total cross section and angular distribution of the process were calculated. As the result of the comparison with the data it was shown that ASR approach provides their good description in the regions far from the pole. Also there was proposed a method allowing to give reasonable description of data in the region of pole within the ASR approach. The strong restrictions for the parameters of the modified ASR approach were obtained. - 17.08.2016
**Ernst-Michael Ilgenfritz (BLTP JINR)**

*"How can lattice QCD describe non-zero baryonic density? Continuation."*pdf

Abstract:

The region of large baryonic density is*terra incognita*in the QCD phase diagram, at least forab initio theoretical investigations usually offered by lattice QCD.

Quenched lattice studies are obviously misleading, and this is known for 20 years when lattice studies with dynamical fermions were turning to the phase structure of QCD. Dynamical studies are possible, however only with decreasing reliability, over a region of limited chemical potential. They give knowledge with controllable precision up to $\mu/T \approx 1$, in other words, they are practically impossible for cold dense matter and matter becoming accessible in heavy ion collisions in the energy range with $\sqrt{s_{NN}}$ between 4 and 10 GeV (so far explored only in the BES extension program at RHIC down to 7.7 GeV). The region of medium temperatures and $\mu/T >> 1$ and $\mu_B=3 \mu_q \sim 0.8$ GeV (according to Cleymans et al. 2006) will become the object of much more dedicated interest in heavy ion collisions planned at facilities like NICA (MPD) and FAIR (CBM). This can be considered as their*brand mark*.

In relatively simple terms, I will give an explanation for the unpleasant situation in lattice theory, which has its roots in the complex phase problem (a.k.a. "sign problem"), which has prevented a broad activity and rapid growth of knowledge (as we were to used to get it for zero baryonic density with $\mu=0$) over the last 10 years.

An intensive search for possibilities to overcome this "technical barrier" has attracted human and machine resources to these methodical questions (detracted away from "number crunching"). This initiative is bearing fruit now and has revealed a number of promising potential escapes. They are all related either to "dualization" (choosing a conjugated configuration space for simulations) or "complexification" (choosing a slightly extended configuration space).

The conference "Lattice 2016" was dominated in a remarkable manner by this development. - 10.08.2016
**Ernst-Michael Ilgenfritz (BLTP JINR)**

*"How can lattice QCD describe non-zero baryonic density?"*pdf

Abstract:

The region of large baryonic density is*terra incognita*in the QCD phase diagram, at least forab initio theoretical investigations usually offered by lattice QCD.

Quenched lattice studies are obviously misleading, and this is known for 20 years when lattice studies with dynamical fermions were turning to the phase structure of QCD. Dynamical studies are possible, however only with decreasing reliability, over a region of limited chemical potential. They give knowledge with controllable precision up to $\mu/T \approx 1$, in other words, they are practically impossible for cold dense matter and matter becoming accessible in heavy ion collisions in the energy range with $\sqrt{s_{NN}}$ between 4 and 10 GeV (so far explored only in the BES extension program at RHIC down to 7.7 GeV). The region of medium temperatures and $\mu/T >> 1$ and $\mu_B=3 \mu_q \sim 0.8$ GeV (according to Cleymans et al. 2006) will become the object of much more dedicated interest in heavy ion collisions planned at facilities like NICA (MPD) and FAIR (CBM). This can be considered as their*brand mark*.

In relatively simple terms, I will give an explanation for the unpleasant situation in lattice theory, which has its roots in the complex phase problem (a.k.a. "sign problem"), which has prevented a broad activity and rapid growth of knowledge (as we were to used to get it for zero baryonic density with $\mu=0$) over the last 10 years.

An intensive search for possibilities to overcome this "technical barrier" has attracted human and machine resources to these methodical questions (detracted away from "number crunching"). This initiative is bearing fruit now and has revealed a number of promising potential escapes. They are all related either to "dualization" (choosing a conjugated configuration space for simulations) or "complexification" (choosing a slightly extended configuration space).

The conference "Lattice 2016" was dominated in a remarkable manner by this development. - 7.07.2016
**E.E. Kolomeitsev (Matej Bel University, Slovakia)**

*"Constraints on the nuclear equation of state. Hyperon puzzle of neutron stars"*pdf

Abstract:

Measurements of neutron stars with masses larger or about 2 solar masses imply that the nuclear equation of state (EoS) should be sufficiently stiff. The stiffness of the Eos is however restricted from above by the constraint from the analysis of particle flow in heavy-ion collisions. The dilemma sharpens if hyperons are included. Since Lambdas and Xi baryons experience attractive potentials in nuclear matter at the saturation density, a naive extrapolation of these potentials would lead unavoidably to the appearance of hyperons in neutron star interiors. That would soften the EoS and lead to the contradiction with the observable star masses (so-called hyperon puzzle). We show that this problem can be resolved if one takes into account a reduction of the mass of the phi meson which mediates a repulsion among hyperons. We propose a relativistic mean-field model with hadron masses and coupling constants depending on the scalar field. All hadron masses undergo a universal scaling, whereas the coupling constants are scaled differently. The appearance of hyperons in dense neutron star interiors is accounted for. The equation of state satisfies well the constraints known from analyses of the astrophysical data and particle production in heavy-ion collisions. - 16.06.2016
**Anastasia Golubtsova (BLTP JINR)**

*"Evolution of holographic Wilson loops in anisotropic quark-gluon plasma"*pdf

Abstract:

In this talk we discuss the evolution of Wilson loops in anisotropic quark-gluon plasma using the holographic approach. We evaluate the Wilson loops in both static and time-dependent cases. The anisotropic time-dependent plasma is dual to Lifshitz-Vaidya background, while we use a black brane in the Lifshitz-like spacetime for a finite temperature plasma in equillibrium. To probe the system we calculate Wilson loops oriented in different spatial directions. We find that anisotropic effects in the Lifshitz-like backgrounds are more visible for the Wilson loops lying in the transversal direction unlike the Wilson loops partially oriented in the longitudinal one. - 11.05.2016
**Andrey Yudin (ITEP, Moscow)***"Neutrino Signal from Collapsing Supernovae"*pdf ppt

"Нейтринный сигнал от коллапсирующих сверхновых"

Abstract:

В докладе будет рассказано о последней стадии эволюции массивных звезд, заканчивающейся коллапсом ядра и взрывом звезды как сверхновой. Рассмотрены основные наблюдательные факты о таких событиях. Важнейшей нерешенной проблемой астрофизики сверхновых в настоящее время является вопрос о механизме взрыва. Именно нейтринный сигнал является уникальным источником информации о процессах, протекающих в первые моменты взрыва в экстремальных условиях коллапсирующего ядра. Будет рассказано о "стандартном" механизме взрыва и "стандартном" нейтринном сигнале, а также о различных существующих альтернативах. Особое внимание будет уделено знаменитой сверхновой SN1987A, нейтринный сигнал от которой, полученный на ряде подземных детекторов, до сих пор является единственным случаем регистрации нейтрино от сверхновых. Кроме того, будет рассказано о возможной "экзотике" при взрыве сверхновой: образование кварковой или гибридной звезды, рождение стерильных нейтрино, и о наблюдательных следствиях, позволяющих проверить эти гипотезы, в частности, по особенностям нейтринного сигнала. - 04.05.2016
**Maxim Andreichikov (ITEP, Moscow)***"Mass spectra of hadrons in strong magnethic field" pdf*

"Массовые спектры адронов в сильном магнитном поле"

Abstract:

Mass spectra of neutral mesons and baryons in a strong magnetic field are considered. The spectra are obtained by means of the vacuum correlators approach and by taking into account confinement and perturbative corrections. The results are compared with the lattice calculations.Рассматриваются массовые спектры нейтральных мезонов и барионов в сильном магнитном поле, полученные с помощью метода вакуумных корреляторов с учетом конфайнмента и пертурбативных поправок. Сравнение с решеточными расчетами.

- 20.04.2016
**A. Yu. Kotov (ITEP, Moscow)**

*"Study of the influence of external effects on the properties of QCD by means of lattice simulation"*pdf

*"Изучение влияния внешних воздействий на свойства КХД методами решеточного моделирования"*(по материалам кандидатской диссертации)

Abstract:

The author of the thesis, A. Yu. Kotov, will present the main results of his PhD dissertation "Modelling the influence of external effects on the properties of QCD by means of lattice simulation".

In particular, the following questions will be discussed:

-- lattice calculation of the viscosity of the quark-gluon plasma including its dependence on temperature

-- first results concerning the properties of two-color QCD with non-vanishing baryon density

-- study of the phase diagram of QCD with non-vanishing chirality imbalance -- lattice study of an exotic superconducting phase of QCD under the influence of very strong magnetic fields.В докладе будут представлены основные результаты кандидатской диссертации Котова А. Ю. “Моделирование влияния внешних воздействий на свойства КХД на решетке”. В частности, будут обсуждаться следующие вопросы: -- решеточное вычисление вязкости в кварк-глюонной плазме, в том числе ее зависимости от температуры;

-- первые результаты изучения свойств двухцветной квантовой хромодинамики с ненулевой барионной плотностью;

-- изучение фазовой диаграммы квантовой хромодинамики с ненулевой киральной плотностью;

-- решеточное изучение экзотической сверхпроводящей фазы квантовой хромодинамики в сверхсильных магнитных полях. - 19.04.2016
**Atsushi Nakamura (Far East Fed. Univ., Vladivostok, Russia; Hiroshima Univ., Japan; RCNP, Osaka Univ., Japan; Nishina Center, RIKEN, Wako/Saitama, Japan)**

*"Study of QCD Phase Diagram by Heavy Ion Experiments and Lattice QCD Experiments"*pdf

Abstract:

To explore the QCD phase structure, we must study QCD at finite temperature and density. A first-principle calculation, lattice QCD, is expected to provide essential information, but it suffers from the so-called the sign problem. The fundamental tool of lattice QCD is Monte Carlo simulation of a path integral, but the measure is complex at finite chemical potential.

In order to avoid this problem, I propose a canonical approach, in which the grand partition function, $Z(\mu,T)$, is expanded as a polynomial of the fugacity, $\xi=\exp(\mu/T)$, where $\mu$ and $T$ are chemical potential and temperature, respectively: $Z(\mu,T) = \sum_n Z_n(T) \xi^n$, and $Z_n(T)$ are the canonical partition functions.

Canonical partition functions are related to the net baryon distribution, which are measured in high energy nuclear reactions, although the experimentally measured quantity is the net-proton distribution. Nevertheless, the net-proton multiplicity may be a proxy of the net baryon distribution. Other observables, such as the net-charge fluctuation and the net-strangeness fluctuation, can be measured both in nuclear and lattice experiments. - 11.04.2016
__D. Ebert__(Humboldt Universit\"at Berlin), T.G. Khunjua (Moscow State University), K.G. Klimenko (IHEP, Protvino), V.C. Zhukovsky (Moscow State University)

*"Competition and duality correspondence between chiral and superconducting channels in (2+1)-dimensional four-fermion models "*pdf

Abstract:

I will explain the duality correspondence between fermion-antifermion and di-fermion interaction channels as established in two (2+1)-dimensional Gross-Neveu type models with a fermion number chemical potential μ and a chiral chemical potential μ_5. The role and influence of this property on the phase structure of the models are investigated. In particular, it is shown that the chemical potential μ_5 promotes the appearance of dynamical chiral symmetry breaking, whereas the chemical potential μ contributes to the emergence of superconductivity.

arXiv:1603.00357 - 24.02.2016
__D. Blaschke__(Wroclaw University, Poland & BLTP JINR),__N.-U. Bastian__(Wroclaw University, Poland)

*"Three-fluid hydro based event simulation for the NICA energy scan and a new EoS with first-order phase transition"*pdf (D. Blaschke), pdf (N.-U. Bastian)

Abstract:

In the first part of the seminar we present first results of simulating the NICA energy scan (\sqrt{s_{NN}}=4-11 GeV) with a new event generator that is based on a three-fluid hydrodynamics description of the early stage of the collision, followed by a particlization at the chemical freezeout to join a UrQMD "afterburner" accounting for hadronic final state interactions. We address the directed flow of protons and pions as well as the proton rapidity distribution for two model equations of state (EoS), with and without a first order phase transition. In the second part we present a recently developed hybrid EoS that fulfills the constraints from compact star phenomenology and describe its advantages over the one used in the simulation up to now. - 18.11.2015
**O. Teryaev,**__R. Usubov__(JINR BLTP)*"Hydrodynamic helicity and handedness in heavy-ion collisions" (in Russian)*pdf

"Гидродинамическая спиральность и киральность (handedness) в соударениях тяжелых ионов"

Abstract:

Завихренность и гидродинамическа спиральность в соударениях тяжелых ионов была изучена в модели Hadron String Dynamics (HSD) посредством моделирования на компьютере. Завихренность рассматривалась для разных моментов времени, подтверждена ее зеркальная структура, установленная ранее в других подходах. Также рассматривается новая величина "киральность" ("handedness") в разных областях пространства в моделях HSD и Parton-Hadron String Dynamics. - 28.09.2015
__E.-M. Ilgenfritz (JINR BLTP)__, V.K. Mitrjushkin (JINR BLTP), I.L. Bogolubsky (JINR LIT), M. Mueller-Preussker (HU Berlin, Germany), V.G. Bornyakov (IHEP Protvino, ITEP Moscow and FEFU Vladivostok) and A. Sternbeck (FSU Jena, Germany)*"Lattice study of gluon and ghost propagators in Landau gauge QCD"*pdf

The talk will be given in connection with the submission of a cycle of publications of the group of authors to the competition for the JINR award 2015.

Abstract:

I will give an overview over intentions and guiding ideas underlying the studies of (gauge dependent) propagators in lattice QCD:

-- confinement criteria formulated in terms of propagators

-- control of assumptions underlying continuum approaches to non-perturbative QCD like Schwinger-Dyson and FRG

-- providing input to continuum approaches to non-perturbative QCD in order to overcome limitations of lattice QCD (e.g. non-vanishing baryonic density)

-- problems and ambiguities preventing a unique fixing of the requested gauge

-- lessons from earlier JINR-Berlin research in the 90-s in the field of lattice QED

-- change of the infrared paradigm from the "scaling solution" to the "decoupling solutions"

-- mapping the non-uniqueness of gauge fixing to the family of ghost boundary conditions specifying the decoupling solutions. - 24.06.2015
**David Blaschke (University Wroclaw (Poland) and BLTP JINR )***"Robustness of the Baryon-Stopping Signal for the Onset of Deconfinement in HIC"*pdf

Abstract:

The impact of the experimental acceptance, i.e. transverse-momentum (p_T) cut-off and limited rapidity region, on the earlier predicted irregularity in the excitation function of the baryon stopping is studied. This irregularity is a consequence of the onset of deconfinement occurring in the compression stage of a nuclear collision and manifests itself as a wiggle in the excitation function of the reduced curvature (C_y) of the net-proton rapidity distribution at midrapidity. It is demonstrated that the wiggle is a very robust signal of a first-order phase transition that survives even under conditions of a very limited acceptance. At the same time the C_y for pure hadronic and crossover transition scenarios become hardly distinguishable, if the acceptance cuts off too much of the low-p_T proton spectrum and/or puts too narrow rapidity window around midrapidity. It is found that the shape of the net-proton rapidity distribution near midrapidity depends on the p_T cut-off. This implies that the measurements should be taken at the same acceptance for all collision energies in order to reliably conclude on the presence or absence of the irregularity. An outlook is given to actual perspectives of this study in relation to the NICA MPD experiment. - 04.06.2015
**A.V. Sadofyev (ITEP, Moscow (Russia) and CTP, Massachusetts Institute of Technology, Cambridge, MA (USA))***"Chiral drag force"*pdf

Joint seminar with "Particle Physics".

Abstract:

We showed that there is an anomalous contribution into the drag force acting on a heavy quark running through the holographic thermal plasma. This contribution results in a correlation between the chiral magnetic effect current and the displacement of heavy quarks in a given event. It is also possible to use the result for further discussion of non-dissipative nature of chiral effects. - 03.06.2015
**Yu. B. Ivanov (NRC "Kurchatov Institute", Moscow)***"Relativistic Heavy-Ion Collisions within Alternative Scenarios: Directed and Elliptic Flow"*pdf

Abstract:

Analysis of the directed flow ($v_1$) and transverse-momentum integrated elliptic flow ($v_2$) in heavy-ion collisions is performed in the range of collision energies \sqrt{s_{NN}} = 2.7--39 GeV. Simulations have been done within a three-fluid model employing a purely hadronic equation of state (EoS) and two versions of the EoS with deconfinement transitions: a first-order phase transition and a smooth crossover transition. High sensitivity of the proton directed flow to the EoS is found. The directed flow indicates that the crossover deconfinement transition takes place in semicentral Au+Au collisions in a wide range of collision energies 4 < \sqrt{s_{NN}} < 20 GeV. The crossover EoS is unambiguously preferable for the description of the most part of experimental data in this energy range. The obtained results suggest that the deconfinement EoS's in the quark-gluon sector should be stiffer at high baryon densities than those used in the calculation. The latter finding is in agreement with that discussed in astrophysics. % Simulations demonstrate low sensitivity of $v_2$ of charged particles to the EoS. All considered scenarios equally well reproduce recent STAR data on $v_2$(charged) for mid-central Au+Au collisions and properly describe its change of sign at the incident energy decrease below \sqrt{s_{NN}} = 3.5 GeV. The predicted integrated elliptic flow of various species exhibits a stronger dependence on the EoS. A noticeable sensitivity to the EoS is found for anti-baryons and, to a lesser extent, for $K^-$ mesons. In particular, the $v_2$ excitation functions of anti-baryons exhibit a non-monotonicity within the deconfinement scenarios that was predicted by Kolb, Sollfrank and Heinz. However, low multiplicities of anti-baryons at \sqrt{s_{NN}}< 10 GeV result in large fluctuations of their $v_2$ which may wash out this non-monotonicity.

- 18.03.2015
**Anna Radovskaya (Lebedev Institute, RAS, Moscow)***"Formation of the equation of state in the early stage of ultrarelativistic heavy-ion collisions"*pdf

Abstract:

We discuss a schematic model describing the evolution of matter created in ultrarelativistic heavy-ion collisions. We employ the Keldysh formalism in order to describe the relaxation of a quantum field from the initial, highly excited state. For the case of a homogeneous scalar field we show the emergence of the equation of state explicitly. We present a complete description of subleading corrections and discuss analytical expressions for some of them. - 26.02.2015
**G.Yu. Prokhorov (Southern Federal University, Rostov-on-Don)***"Dynamics of wave fluctuations in homogeneous and isotropic Yang-Mills field condensate and cosmological phase transition in QCD" (in Russian)*

*"Динамика волновых флуктуаций в однородном и изотропном конденсате полей Янга-Миллса и космологический фазовый переход в квантовой хромодинамике"*pdf

Abstract:

На численном и аналитическом уровне исследована самосогласованная задача о взаимодействии пространственно-неоднородных волновых мод калибровочного поля группы SU(2) с однородным и изотропным конденсатом полей Янга-Миллса. Показано, что это взаимодействие приводит к ранее не известным эффектам перекачки энергии из конденсата в частицы и возбуждению продольной компоненты калибровочного поля. Построенная теория обобщена на случай суперсимметричной модели N=4. Обсуждаются возможности приложения построенной теории к описанию космологического фазового перехода в квантовой хромодинамике в ранней вселенной и к решению проблемы о компенсации отрицательного энергетического вклада квантово-топологического КХД вакуума. - 11.02.2015
**Genis Musulmanbekov (LIT JINR)***"On Production and Polarization of Hyperons in Heavy Ion Collisions. Continuation."*

Abstract:

We discuss a schematic model describing the evolution of matter created in ultrarelativistic heavy-ion collisions. We employ the Keldysh formalism in order to describe the relaxation of a quantum field from the initial, highly excited state. For the case of a homogeneous scalar field we show the emergence of the equation of state explicitly. We present a complete description of subleading corrections and discuss analytical expressions for some of them. - 28.01.2015
**Abdel Nasser Tawfik (MTI University Cairo and Egyptian Center of Theoretical Physics)***"Transport Coefficients from SU(3) Polyakov Linear-sigma Model"*pdf

Abstract:

In the mean field approximation, the grand potential of SU(3) Polyakov linear-$\sigma$ model (PLSM) is analysed for the light and strange chiral phase-transition, $\sigma_l$ and $\sigma_s$, respectively and for the deconfinement order parameters $\phi$ and $\phi^*$. Furthermore, the subtracted condensate $\Delta_{l,s}$ and chiral order-parameters $M_b\,$ are compared with the lattice QCD calculations. By using the dynamical quasi-particle model (DQPM), which can be considered as a system of noninteracting massive quasi-particles, we have evaluated the decay width and the relaxation time of quarks and gluons. In framework of LSM and when including Polyakov corrections, the interaction measure $\Delta/T^4$, the specific heat $c_v$ and speed of sound squared $c_s^2$ have been determined. Furthermore, the thermal evolution of the normalized quark number $n_q/T^3$ and the susceptibilities $\chi_q/T^2$ at different baryon chemical potentials are confronted with the corresponding Stefan-Boltzmann (SB) limits. The electric $\sigma_e$ and heat $\kappa$ conductivity and their ratio are compared with the available lattice QCD calculations. The bulk and shear viscosities normalized to the thermal entropy $\xi/s$ and $\eta/s$, respectively, and the ratio of bulk and shear viscosities are evaluated from PLSM compared with the lattice QCD data. Finally, the ratios $(\xi /s)/(\sigma_e T)$ and $(\eta /s)/(\sigma_e T)$ are calculated. - 21.01.2015
**David Blaschke (JINR BLTP and Univ. Wroclaw, Poland)***"Quantum flavor kinetics and chemical freeze-out"*pdf

Abstract:

We present current status of a quantum kinetic formulation of the chemical equilibration process in dense hadronic matter at the hadronization transition. Delocalization of hadron wave functions at the Mott-Anderson transition (where their binding energies vanish) lead to a divergence of scattering lengths and critical enhancement of rearrangement collisions between hadrons. We exemplify this for different meson-meson scattering processes from light (pi-pi scattering) to heavy flavors (charmonium dissociation). On this basis we suggest that chemical freeze-out has to be correlated with (partial) chiral symmetry restoration. - 17.12.2014
**Martin Kirakosyan (Lebedev Physical Institute of RAS, Moscow)***"Collective effects in ultrarelativistic nuclei collisions" (in Russian)*pdf

"Коллективные эффекты в столкновениях ультрарелятивистских ядер"

Abstract:

Доклад посвящен результатам представленным в готовящейся к защите кандидатской диссертации автора. Будут обсуждаться феномен черенковского излучения глюонов в сильновзаимодействующей среде, турбулентные вклады в поляризацию кварк-глюонной плазмы, а также феноменология потерь на переходное излучение на случайных неоднородностях в среде, образующейся в результате столкновения ядер. - 12.11.2014
**Genis Musulmanbekov (LIT JINR)***"On Production and Polarization of Hyperons in Heavy Ion Collisions."*ppt

Abstract:

A new mechanism is explained for the interpretation of the non-monotonic, enhanced yield of hyperons and strange mesons (also known as "horn" effect), that is observed in central heavy ion collisions in the experiment NA49 at SPS and confirmed by STAR at RHIC. We argue that the data indicate the transition of the nucleons in the overlap region of the colliding nuclei with high nuclear density into a certain hyperon phase. In semicentral heavy ion collisions a strong magnetic field and very large orbital angular momentum can be created. The polarization of hyperons becoming possible due to these phenomena is discussed. - 03.09.2014
**Elena Bratkovskaya (ITP & FIAS, Uni. Frankfurt)***"Electromagnetic probes of the QGP."*pdf

Abstract:

A review of the latest theoretical results on electromagnetic probes (direct photons and dileptons) of the QGP in heavy-ion collisions at ultra-relativistic energies will be presented. While the dilepton spectra at low invariant mass show in-medium effects like a collisional broadening of the vector mesons in their spectral functions, the dilepton yield at high invariant masses (above 1.1 GeV) is dominated by the QGP contributions for central heavy-ion collisions at ultra-relativistic energies. Also we discuss the present status of the photon $v_2$ "puzzle" - one of the challenging topics related to the large elliptic flow $v_2$ of the direct photons experimentally observed at RHIC and LHC energies. It turns out that the photonic $v_2$ is as large as the hadronic $v_2$, whereas many models predict a very small $v_2$ of photons from the QGP due to their early emission before the system has developed a sizeable momentum anisotropy. We investigate the role of hadronic and partonic sources for the photon spectra as well as the possibility to subtract the QGP signal from the experimental observables by studying the centrality dependence of the direct photon yield. - 27.08.2014
**Igor Mishustin (Frankfurt Institute for Advanced Studies, Goethe University, Frankfurt/Main, Germany and National Research Center "Kurchatov Institute", Moscow, Russia)***"Non-equilibrium Dynamics of the Chiral/Deconfinement Phase Transition."*pdf

Abstract:

Observable signals of possible QCD phase transitions are strongly influenced by the rapid non-equilibrium dynamics during a heavy-ion collision. In order to realistically estimate these effects we have developed a non-equilibrium chiral fluid dynamics model, where the quark-antiquark fluid is dynamically coupled to the order-parameter fields. The model takes into account dissipation and fluctuation effects stemming from the interaction between the fluid and the fields. The actual calculations are done within the linear sigma model with constituent quarks, coupled to the Polyakov loop. The dynamical trajectories of the fluid elements on the T-\mu plane are studied for different types of the phase transition. The effects of supercooling and reheating are clearly observed in the case of a first-order phase transition. In this case we see the formation of domains in net-baryon density due to spinodal decomposition. They should lead to an enhancement of higher harmonics in azimuthal distributions of net-baryons. It is also demonstrated that long-wavelength fluctuations near the critical point show a strong enhancement only in a quasi-static system, but they are suppressed in the case of a fast expansion. - 09.07.2014
**Ernst-Michael Ilgenfritz (VBLHEP & BLTP, JINR Dubna) (tmfT collaboration)***"Thermal crossover, propagators and equation of state from N_f=2 and N_f=2+1+1 flavors dealt within the twisted mass approach."*

Abstract:

A relative majority of European lattice simulations of full QCD have got concentrated on the twisted mass approach to Wilson fermions (Collaboration ETMC) as opposed to other (staggered, clover improved Wilson, domain wall etc.) fermion formulations. The "twisted mass at finite temperature" (tmfT) collaboration is a small group of authors following this approach for simulations at finite temperature, in particular using the results of ETMC (at a set of unphysical pion masses) at zero temperature as input for calibration. Finite temperature simulations have been performed in order to explore the nature of the phase transition with two degenerate light flavors (u and d) in the chiral limit and to find the temperature of the crossover for the physical pion mass. As a continuation of previous work of the BLTP-Humboldt University collaboration on Landau gauge gluon and ghost propagators at T=0, finite-temperature configurations have been used to study the T dependence of the electric and magnetic gluon propagators in the vicinity of the crossover. These results are connected with our earlier corresponding quenched results near to the phase transition of SU(3) pure gauge theory via the Dyson-Schwinger approach (Ch. Fischer). The twisted-mass approach with an additional non-degenerate quark doublet, tuned to realistic s and d quark masses, will be described. The status of results concerning the temperature of the crossover for would-be pion masses between 220 and 400 MeV and the contributions of light and heavy quarks to the equation of state will be reported. - 07.07.2014
**Alexander Botvina (INR-RAS, Moscow, Russia, and FIAS, Frankfurt/Main, Germany)***"Production of hypernuclei from excited nuclear residues in relativistic ion collisions: New opportunities for BM@N and MPD@NICA."*pdf

Abstract:

Investigation of hypernuclei is a rapidly progressing field of nuclear physics, since they give opportunities both to improve methods of traditional nuclear studies and to open new horizons for studying particle physics and nuclear astrophysics. Within dynamical and statistical theories we study the main regularities in the production of hypernuclei emerging from the projectile and target residues in relativistic ion collisions. This process will allow to study the mechanisms of peripheral collisions and the properties of hyper-matter of low temperatures, including hyperon-hyperon interactions at low energies. We demonstrate that the yields of hypernuclei increase considerably at beam energies above the energy threshold for Lambda hyperons (~1.6 AGeV), followed by a saturation for yields of hypernuclei with increasing the beam energy up to few TeV [1]. These hypernuclei have a broad distribution in masses and isospin. They can even reach beyond the neutron and proton drip-lines since they are stable with respect to nucleon emission [2]. Weak decay of such hypernuclei may lead to formation of normal nuclei beyond the drip-lines also, thus providing a unique chance for reaching island of stability on the nuclear chart. The production of specific hypernuclei depend strongly on the isotopic composition of the projectile, therefore, it will be possible to obtain exotic hypernuclei that may be difficult to reach in traditional hypernuclear experiments [1]. We also show new calculations including DCM, UrQMD, and HSD models with formation of light hypernuclei of all rapidities and large hyper-residues, which can be obtained in the fixed-target experiments. The perspectives of hypernuclear studies involving these novel processes at the present accelerators are discussed.

[1] A.S. Botvina, K.K. Gudima, and J. Pochodzalla, Phys. Rev. C88, 054605 (2013).

[2] N. Buyukcizmeci, A.S. Botvina, J. Pochodzalla, and M. Bleicher, Phys. Rev. C88, 014611 (2013). - 28.05.2014
**Masayasu Hasegawa (BLTP JINR)***"Chiral symmetry and overlap fermions, instantons and monopoles in lattice QCD".*

Abstract:

At the end of the 90-s it became clear that overlap fermions realize chiral symmetry to a maximal degree permitted by lattice discretization. This has opened the way to study the relation between chiral and topological aspects of QCD vacuum structure. It is known -- to a large extent due to the work of the Kanazawa-DESY-ITEP collaboration on one hand and of the Pisa group on the other -- that monopoles play a crucial role in the confinement mechanism through monopole condensation and dual superconductivity. Whereas instantons offer a beautiful mechanism for spontaneous breaking of chiral symmetry, a direct relation to confinement is not obvious. The purpose of the present study reported in this seminar is to show a relation between instantons and monopoles by using the overlap fermions as an analytical tool. One non-trivial problem is to relate them, despite the different dimensionality of instantons (4-dimensional event-like) and monopoles (3-dimensional particle-like). The exact relation remained unclear in spite of many studies. Therefore we try to clarify the relation with the help of overlap fermions on the lattice. In this seminar, first I will introduce the overlap fermions briefly. Second, I will explain how to create an additional monopole to a given lattice configuration. Third, I will give some results showing that this construction is consistent. Finally, I will present some new results clarifying the relation between instantons and monopoles. - 14.05.2014
**Ludmila Malinina (SINP MSU - JINR)***"Femtoscopy of heavy ion and pp collisions at high energies."*pdf

Abstract:

The femtoscopic correlations allow one to measure the space-time characteristics of particle production thanks to the effects of quantum statistics for identical particles and final state interactions for both identical and non-identical ones. The main features of the femtoscopy measurements in heavy-ion collisions at SPS and RHIC are i) the value of the radii almost independent on the beam energy, ii) the increase of the correlation radii with increasing multiplicity of events and iii) the decrease of the radii with increasing of pair transverse momentum. These are understood as a manifestation of the strong collective flow. Such effects were also observed at the LHC with the interferometry volume increased twice compared with RHIC. The data from Pb-Pb collisions and its comparison with the dynamical models will be presented. The high multiplicity pp collisions reach particle densities comparable to the ones measured in peripheral Cu-Cu and Au- Au collisions at RHIC so it is natural to investigate collective behaviour in pp. The similarities and differences between pp and heavy-ion data are discussed. - 7.05.2014
**Hans-Peter Pavel (TU Darmstadt & BLTP JINR Dubna)***"Low energy QCD in terms of gauge invariant dynamical variables"*pdf

Abstract:

Using a generalized polar decomposition of the gauge fields into gauge-rotation and gauge-invariant parts, which Abelianises the Non-Abelian Gauss-law constraints to be implemented, a Hamiltonian formulation of low energy QCD in terms of gauge invariant dynamical variables can be achieved. The exact implementation of the Gauss laws reduces the colored spin-1 gluons and spin-1/2 quarks to unconstrained colorless spin-0, spin-1, spin-2 and spin-3 glueball fields and colorless Rarita-Schwinger fields respectively. The obtained physical Hamiltonian naturally admits a systematic strong-coupling expansion in powers of $\lambda=g^{-2/3}$, equivalent to an expansion in the number of spatial derivatives. The leading-order term corresponds to non-interacting hybrid-glueballs, whose low-lying spectrum can be calculated with high accuracy by solving the Schroedinger-equation of the Dirac-Yang-Mills quantum mechanics of spatially constant fields (at the moment only for the 2-color case). The discrete glueball excitation spectrum shows a universal string-like behaviour with practically all excitation energy going in to the increase of the strengths of merely two fields, the "constant Abelian fields" corresponding to the zero-energy valleys of the chromomagnetic potential. Inclusion of the fermionic degrees of freedom significantly lowers the spectrum and allows for the study of the sigma meson. Higher-order terms in $\lambda$ lead to interactions between the hybrid-glueballs and can be taken into account systematically using perturbation theory in $\lambda$, allowing for the study of IR-renormalisation and Lorentz invariance. The existence of the generalized polar decomposition used, the position of the zeros of the corresponding Jacobian (Gribov horizons), and the ranges of the physical variables can be investigated by solving a system of algebraic equations. Its exact solution for the case of one spatial dimension and first numerical solutions for two and three spatial dimensions indicate that there is a finite number of solutions separated by Gribov horizons. - 23.04.2014
**G.M. Zinovjev (BITP, Kiev),**__S.V. Molodtsov__(BLTP, JINR)*"Quark ensembles with infinite correlation length" (in Russian)*pdf

"Кварковые ансамбли с бесконечной корреляционной длиной"

Abstract:

Рассматривается ряд точно интегрируемых (кварковых) моделей квантовой теории поля с бесконечной корреляционной длиной. Отмечается неустойчивость стандартного вакуумного кваркового ансамбля - моря Дирака (в случае пространственно-временной размерности выше трех), связанная с сильной вырожденностью состояния, которая обусловлена характером распределения по энергии. При стремлении параметра обрезания по импульсу к бесконечности распределение становится бесконечно узким, приводящим к большим (неограниченным) флуктуациям. Проводится сравнение различных вакуумных ансамблей: моря Дирака, нейтрального ансамбля, цветового сверхпроводника и БКШ состояния. В случае цветового кваркового взаимодействия, делается однозначный выбор в пользу БКШ состояния, как основного состояния кваркового ансамбля.

На основе работы: pdf - 16.04.2014
**Iu. A. Karpenko (FIAS, Frankfurt & BITP, Kiev)***"Beam energy scan using a viscous hydro+cascade model "*pdf

Abstract:

Following the experimental program at BNL/RHIC, we perform a similar "energy scan" using 3+1D viscous hydrodynamics coupled to the UrQMD hadron cascade, and study the collision energy dependence of pion and kaon rapidity distributions and m_t-spectra, as well as charged hadron elliptic flow. To this aim the equation of state for finite baryon density from a Chiral model coupled to the Polyakov loop is employed for hydrodynamic stage. 3D initial conditions from UrQMD are used to study gradual deviation from boost-invariant scaling flow. We find that the inclusion of shear viscosity in the hydrodynamic stage of evolution consistently improves the description of the data for Pb-Pb collisions at CERN SPS, as well as of the elliptic flow measurements for Au-Au collisions in the Beam Energy Scan (BES) program at BNL/RHIC. The suggested value of shear viscosity is \eta_s>0.2 for \sqrt{s}=6.3...39 GeV. - 19.03.2014
**I. Ya. Aref'eva (Mathematical Institute, RAS, Moscow)***"Holographic description of quark-gluon plasma"*ppt

Abstract:

The holographic description of the quark-gluon plasma permits, in principle, to find the interquark interaction and the meson spectrum, the thermalization time, the multiplicity of particles being produced, as well as the hydrodynamical characteristics of the quark-gluon plasma produced in heavy-ions collisions. There are several holographic models providing these physical quantities. The problem of finding a holographic model that simultaneously gives reasonable values for all these phenomenological parameters will be discussed. - 19.02.2014
**B.V. Batyunya (JINR, VBLHEP)***"ALICE (A Large Ion Collider Experiment) results from the LHC"*pdf

Abstract:

The following results are considered for p-p, p-Pb and Pb-Pb collisions:

-Event multiplicity,

-Particle species ratios and spectra,

-Nuclear modification factor for charged particles and heavy Quarkonia,

-Resonance production,

-Bose-Einstein Correlations (Femtoscopic Correlations),

-Azimuthal anisotropic flow.

I shall compare with other experiments and theoretical predictions. The results are discussed from the point of view of collective effects and the generation of Quark-Gluon-Plasma in Heavy Nuclear Collisions. - 29.01.2014
**M.V. Altaisky (Space Research Institute RAS)***"Perspectives of wavelet bases in simulation of lattice theories"*pdf

Abstract:

We consider the perspectives of using orthogonal wavelet expansion with Daubechies wavelets for lattice theories. The discrete wavelet transform have been already applied to simulate the Landau-Ginzburg/Ф4 theory with the assumption that the wavelet coefficients of the order parameter Ф(x) are delta-correlated Gaussian processes in the scale-position space. This reduces the autocorrelation time of simulation, and is not the only merit of wavelet transform. By construction the wavelet transform represents the snapshot of a field at a given scale, and therefore can be used as a tool to study the correlations between fluctuations of different scales. For the same reason the relation of wavelet transform to the renormalization group are considered. We also discuss the prospective of wavelet transform to improve the Metropolis algorithm and the simulated annealing procedure. - 22.01.2014
**Victor Braguta (IHEP Protvino and ITEP Moscow)***"Study of the axial magnetic effect"*pdf

Abstract:

An axial magnetic field, which couples to left- and right-handed fermions with opposite signs, may generate in equilibrium a dissipationless steady energy flow of fermions in the direction of the field even, in the presence of interactions. We report on a numerical observation of this Axial Magnetic Effect in quenched SU(2) lattice gauge theory. We find that in the deconfinement (plasma) phase the energy flow grows linearly with the increase of the strength of the axial magnetic field. In the confinement (hadron) phase the Axial Magnetic Effect is absent. The temperature dependence of the Axial Magnetic effect is studied. - 15.01.2014
**Maxim Ulybyshev (Lomonosov Moscow State University, Institute for theoretical problems of microphysics and ITEP Lattice Group)***"Chiral symmetry breaking in graphene: a lattice study of excitonic and antiferromagnetic phase transitions."*pdf ppt

Abstract:

I'll present a review of lattice simulations of graphene electronic properties. Graphene is an example of a system with strongly correlated electrons which can be described in the low-energy limit by an effective field theory with very large coupling constant. Therefore it can be a subject of spontaneous symmetry breaking with the appearance of various fermionic condensates. The simulations of graphene electronic properties can be divided into two branches: 1) calculations within the framework of graphene effective field theory (2 flavours of (2+1)-dimensional massless Dirac fermions strongly interacting with ordinary (3+1)-dimensional electromagnetic field); 2) simulations of the original tight-binding model on a hexagonal lattice. Each method has its own advantages and disadvantages. The main difference between them are the appearance of different order parameters that correspond to antiferromagnetic and excitonic phase transitions, correspondingly. I'll give the review of both approaches emphasizing the relations between them: how the results of calculations in the low-energy effective field theory can be compared with the results of simulations on the hexagonal lattice which take into account the "ultraviolet" behaviour of quantum fields. - 18.12.2013
__D. B. Blaschke__, G. A. Contrera, A. G. Grunfeld*"Phase diagrams in nonlocal Polyakov-NJL models constrained by Lattice QCD results."*pdf

Abstract:

Based on lattice QCD-adjusted SU_f(2) nonlocal Polyakov-Nambu-Jona-Lasinio (PNJL) models, we investigate how the location of the critical endpoint in the QCD phase diagram depends on the strength of the vector meson coupling, as well as on the Polyakov-loop (PL) potential and the form factors of the covariant interaction model model. These are constrained by lattice QCD data for the quark propagator. The strength of the vector coupling is adjusted such as to reproduce the slope of the pseudocritical temperature for the chiral phase transition at low chemical potential extracted recently from lattice QCD simulations. Our study supports the existence of a critical endpoint in the QCD phase diagram albeit the constraint for the vector coupling shifts its location to lower temperatures and higher baryochemical potentials than in the case without it. - 13.11.2013
**R.G. Nazmitdinov (BLTP JINR)***"Elements of Random Matrix Theory and chaos-order transition in finite quantum systems. Continuation."*ppt

Abstract:

We briefly discuss basic elements of Random Matrix Theory which can be used for analysis of spectra of many-body systems. Considering different systems such as atomic nuclei, quantum dots and quantum billiards, we demonstrate the universality of the Random Matrix approach as a tool to detect the chaos-order transition in finite Fermi systems. It is shown that this transition occurs at certain conditions which give rise to dynamical symmetries in chaotic dynamics of fermions. - 06.11.2013
__Boris V. Martemyanov__(ITEP, Moscow) and E.-M. Ilgenfritz (JINR) and M. Müller-Preussker (HU Berlin)*"Topological structure of gluodynamics close to the transition temperature studied in the IR by low modes of the overlap Dirac operator"*pdf

Abstract:

Topological objects of SU(3) gluodynamics near the transition temperature are studied at the infrared scale with the help of zero and near-zero modes of the overlap Dirac operator. We construct the UV filtered topological charge density in three versions by choosing different temporal boundary conditions applied to this operator. In the reference case of analytical (anti)caloron solutions the zero modes would be located, correspondingly, on three types of constituent dyons (antidyons), which can be considered as the elusive ``instanton quarks''. Clustering of the three topological charge densities marks the positions of dyons and antidyons which are approximately recognizable in equilibrium (Monte Carlo) gluonic field configurations. We classify them either as constituents of nondissociated (anti)calorons or as constituents of (anti)dyon pairs or as isolated (anti)dyons. The pattern of the Polyakov loop, as it is found inside these clusters after a small number of overimproved cooling steps, resembles predictions made for analytical caloron solutions. - 30.10.2013
**Andrey Kotov (ITEP)***"Non-perturbative study of the viscosity in SU(2) lattice gluodynamics"*pdf

Abstract:

A calculation of the viscosity of the gluon plasma has been performed by lattice simulation of $SU(2)$ gluodynamics on supercomputers. The calculation focuses on a temperature of $T/T_c=1.2$ . The evaluation is based on the Kubo-formula relating the viscosity to the spectral function of the correlation function of the energy-momentum tensor. Problems of the analytical continuation from Euclidean data to the real-time spectral function are discussed. - 23.10.2013
**D.N. Voskresensky (NRNU "MEPhI")***"Neutrino cooling of neutron stars"*ppt

Abstract:

It will be argued that neutrino emission from dense hadronic component in neutron stars is subject of strong modifications due to collective effects in the nuclear matter. With the most important in-medium processes incorporated in the cooling code an overall agreement with available X-ray data including new data on Cassiopea A and data on neutron star masses can be achieved. - 16.10.2013
**Elena V. Luschevskaya (ITEP)***"The \rho and A mesons in a strong abelian magnetic field in SU(2) lattice gauge theory"*pdf

Abstract:

The correlators of vector, axial and pseudoscalar currents have been calculated in the background of a strong abelian magnetic field in $SU(2)$ gluodynamics simulated with an improved gauge action. The neutral $\rho$ and $A$ meson masses with different spin projections to the axis parallel to the external magnetic field ${\vec B}$ have been calculated. The masses of the neutral mesons with zero spin $S = 0$ decrease with increasing strength of the magnetic field. The masses of the $\rho$ and $A$ mesons with spin $S = \pm 1$ increase with the value of $|{\vec B}|$. The mass extrapolation and renormalization also were performed on the lattice. - 02.10.2013
**Andrey Leonidov (Lebedev Institute of Physics, RAS, Moscow)***"Turbulent polarization in QED and QCD plasma"*pdf

Abstract:

The possibility of turbulent behavior of dense matter created in ultrarelativistic heavy ion collisions and its experimental manifestations has recently drawn coniderable attention. In the talk, after a brief introduction to possible turbulence-related phenomena in heavy ion collisions, we focus on recent results on polarization properties of Abelian and non-Abelian turbulent ultrarelativistic plasma. In particular, we discuss possible turbulence-related instabilities and turbulent modification of plasmon properties. - 25.09.2013
**R.G. Nazmitdinov (BLTP JINR)***"Elements of Random Matrix Theory and chaos-order transition in finite quantum systems"*

Abstract:

We briefly discuss basic elements of Random Matrix Theory which can be used for analysis of spectra of many-body systems. Considering different systems such as atomic nuclei, quantum dots and quantum billiards, we demonstrate the universality of the Random Matrix approach as a tool to detect the chaos-order transition in finite Fermi systems. It is shown that this transition occurs at certain conditions which give rise to dynamical symmetries in chaotic dynamics of fermions. - 14.08.2013
**Nodar Shubitidze (LHEP JINR)***"On more accurate evaluations of three- and four-particle phase-space integrals" (in Russian)*ppt

"К более точному вычислению трех- и четырех-частичного фазово-пространственного интеграла"

Аннотация:

Представлены интегральные формы для вычисления трех- и четырех-частичных фазово-пространственных интегралов. Получены нерелятивисткие и ультрарелятивистские пределы. Полученные формулы позволяют более быстро и легко вычислять соответствующие интегралы. - 07.08.2013
**Elena Bratkovskaya (ITP&FIAS, Univ. Frankfurt)***"The properties of parton-hadron matter from heavy-ion collisions"*pdf

Abstract:

The intriguing problem of modern high energy and heavy-ion physics is to understand the nature of deconfinement and the phase transition from hadronic to partonic matter - the Quark-Gluon Plasma (QGP)- which occurs during heavy-ion collisions at relativistic energies. The latest experimental findings at high energy heavy-ion collisions indicate that the QGP shows the properties of a strongly interacting liquid (sQGP) rather than - as expected initially - a weakly interacting gas of partons. From the other hand, at low energy one observes a significant modification of hadronic properties in dense and hot nuclear environment. An overview of experimental observables as well as theoretical models for the dynamical description of strongly interaction parton-hadron matter in- and out-off equilibrium will be presented, the perspectives for the future NICA and BM@N experiments will be discussed. - 03.07.2013
__Sergei Nedelko__(BLTP JINR), Vladimir Voronin (BLTP JINR & Dubna Uni.)*"A Domain Wall Network as QCD Vacuum: Confinement, Chiral Symmetry, Hadronization"*pdf

Abstract:

An overall task pursued by most of the approaches to QCD vacuum structure is an identification of the properties of nonperturbative gauge field configurations able to provide a coherent resolution of the confinement, the chiral symmetry breaking, the $U_{\rm A}(1)$ anomaly and the strong CP problems, both in terms of color-charged fields and colorless hadrons. The central subject of the talk is an ensemble of almost everywhere homogeneous, Abelian and (anti-)self-dual gluon field configurations. These configurations are represented by a network of domain wall defects in an initially homogeneous background. A single domain wall is given by the sine-Gordon kink configuration for the angle between the chromomagnetic and chromoelectric components of the gauge field. The kink arises as a solution of the effective equations of motion within the Ginzburg-Landau approach to the effective quantum action of QCD. The effective action takes into account the existence of a non-vanishing gluon condensate $\langle g^2F^2\rangle$ and the symmetries of QCD. The network of domain walls is introduced by a combination of multiplicative and additive superpositions of kinks. The spectrum and eigenmodes of color charged field fluctuations are calculated for the case of an infinitely thin planar Bloch domain wall. The character of the spectrum and eigenmodes of field fluctuations in the presence of the network of domain walls characterizes the QCD vacuum as the heterophase mixed state. The concept of the confinement-deconfinement transition in terms of the ensemble of domain wall networks is outlined. The role of a strong electromagnetic field as a trigger of deconfinement is discussed. This ensemble of gluon fields provides a setup for description of the main nonperturbative features of QCD. The phenomenological results obtained previously in the context of domain model are reviewed: confinement of static and dynamical quarks, chiral symmetry realization, the $U_A(1)$ anomaly and the strong CP problem, as well as the mechanism of hadronization. In particular, with a minimal set of parameters (characteristic for QCD) the model describes the properties of mesons from qualitatively different parts of the spectrum: light mesons (including the Regge spectrum), heavy quarkonia, heavy-light mesons, electromagnetic form factors and decay constants. - 26.06.2013
**Yongseok Oh (Kyungpook National University, Korea)***"Skyrmions with vector mesons: single Skyrmion and baryonic matter"*pdf

Abstract:

The roles of light $\omega$ and $\rho$ vector mesons in the Skyrmion are investigated in a chiral Lagrangian derived from hidden local symmetry (HLS) up to ${\cal O}(p^4)$ including the homogeneous Wess-Zumino terms. We write a general master formula that allows us to determine the parameters of the HLS Lagrangian from a class of holographic QCD models valid at the large-$N_c$ and large-$\lambda$ (`t Hooft constant) limit by integrating out the infinite towers of vector and axial-vector mesons other than the lowest $\rho$ and $\omega$ mesons. Within this approach we find that the physical properties of the Skyrmion as the solitonic description of baryons are independent of the HLS parameter $a$. Therefore the only parameters of the model are the pion decay constant and the vector-meson mass. Once determined in the meson sector, we have a totally parameter-free theory that allows us to study unequivocally the role of light vector mesons in the Skyrmion structure. We find that the inclusion of the $\rho$ meson reduces the soliton mass, which makes the Skyrmion come closer to the Bogomol`nyi-Prasad-Sommerfield soliton, but the role of the $\omega$ meson is found to increase the soliton mass. This model is also applied to investigate baryonic matter as Skyrmion crystals. - 03.06.2013
**Mridupawan Deka (BLTP JINR)***"Meta-stable States in the Quark-Gluon Plasma"*pdf

Abstract:

In pure $SU(3)$ gluodynamics, the deconfined phase exists in three degenerate states which are related to each other via $Z(3)$ rotations. For QCD with dynamical fermions, the $Z(3)$ symmetry is explicitly broken. As a consequence, the degeneracy between the three states is lifted, and one of these states becomes the lowest-lying phase. For asymptotically high temperatures one expects that the effects of quarks can at most render the other two phases meta-stable. In this project (Phys.Rev. D85 (2012) 114505) we have studied the meta-stable phases at high temperature by means of lattice QCD. We have considered $N_f=2$ and $3$ flavours of dynamical staggered quarks, and have carried out simulations at various values of the inverse gauge coupling $\beta$ to observe these states. We have estimated the temperature above which the expected meta-stability appears. - 29.05.2013
**A. V. Friesen (BLTP JINR)***"Scattering of Quarks on Quarks and Hadrons"*pdf

*"Рассеяние кварка на кварке и адроне"*

А. В. Фризен, Ю.Л. Калиновский, В. Д. Тонеев

Abstract:

We discuss the Nambu-Jona-Lasinio model with inclusion of the Polyakov loop (PNJL model). We discuss in particular the parametrization of the effective potential in the gluon sector. A number of new parameters for the effective potential is introduced, which are motivated by an approximation of new lattice data. Then the thermodynamics of this model is studied in detail. The application of this model to the description of mesons and quarks embedded in a hot and dense medium is discussed. In particular, the elastic scattering of quarks with quarks and antiquarks and - for the first time - of quarks with hadrons is studied. Results of numerical calculations for the total and the differential cross section of a quark on a quark, on an antiquark and on a pion will be reported. - 22.05.2013
**Joseph Manjavidze (VBLHEP JINR)***"On S-matrix Interpretation of Thermodynamics"*

Abstract:

The aim of the talk is to point out the connection between ordinary S-matrix theory of the multiple production processes and the real time finite temperature field theory in the sense of Schwinger-Keldysh. It is shown that a one-to-one connection occurs if and only if the event-by-event fluctuations of the mean energy of the produced particles are Gaussian, i.e. the system is in "equilibrium". The established connection (i) defines the thermodynamical parameters of the Schwinger-Keldysh theory through experimental input data and (ii) defines the range of applicability of thermodynamical approaches to the description of multiparticle production processes. - 07.05.2013
**D. E. Alvarez-Castillo (BLTP JINR)***"Symmetry energy in the neutron star equation of state and astrophysical observations"*pdf

Abstract:

A systematic study of the role of the nuclear symmetry energy $E_s(n)$ for the description of neutron star (NS) matter is presented. In a first part, the behavior of $E_s(n)$ at subsaturation densities is discussed which is relevant for the location of the crust-core transition inside the star and thus for the crust thickness. We discuss how observations of glitches for the Vela pulsar constrain the fraction of the crustal moment of inertia and thus $E_s(n)$ at low densities. In a second part the conjecture of a universal symmetry energy contribution to the NS equation of state (EoS) at supersaturation densities is presented. Ths result is derived from the finding that for NS matter the asymmetry contribution to the energy per nucleon (in the parabolic approximation) has a maximum bound as a function of baryon density which corresponds to a proton fraction being almost constant and below the value for the threshold of the Direct Urca (DU) cooling mechanism, i.e., around $x_{\rm DU}\sim 1/8$. As we have safe knowledge that the DU process cannot be operative in a large class of NS, the EoS describing the matter their interior cannot allow proton fractions exceeding $x_{\rm DU}$. This implies the universal behaviour of the symmetry energy contribution which can be exploited for linking the EoS determination by NS observations with that by heavy-ion collision experiments. - 10.04.2013
**Petr Kopnin (ITEP)***"Holographic models of QCD in the strong coupling region."*pdf

Abstract:

We discuss several properties of the strongly coupled QCD in the presence of vacuum condensates and external fields in the framework of holographic AdS/QCD models. We investigate the compatibility of the dual AdS/QCD models with the axial low energy theorems of QCD, demonstrating a method of calculating the spectral density of the Dirac operator in dual models. We also discuss the implications of the holographic models for the QCD dynamics in strong external magnetic fields, such as the chiral magnetic effect, the behavior of the Debye screening mass in quark-gluon plasma in the magnetic field, and the dependence of the magnetic susceptibility and magnetization of the quark condensate on the external fields. The last part of the talk is dedicated to the examination of the Gross-Ooguri phase transition in the Wilson loop correlator in the presence of the gluon condensate. - 03.04.2013
**Irina Aref'eva (Steklov Mathematical Institute)***"Quark-Gluon Plasma Formation in Heavy Ion Collisions in Holographic Description"*pdf

Abstract:

Starting from the discovery of QGP in heavy ions collisions at RICH, a lot of theoretical efforts were applied to describe this phenomena within QCD frameworks. The main problem is that this phenomena is dynamical and in same time essentially nonperturbative. AdS/CFT correspondence, which appeared as a formal duality between the $N=4$ super Yang--Mills theory and quantum gravity in the AdS background, has become a powerful tool for studying various properties of real physical systems in the strong-coupling limit. The appearance of the quark-gluon plasma after the heavy-ion collision in dual terms is described as formation of a black hole. We discuss two holographic dual models of thermalization. In the first one colliding ions are described by gravitational shock waves in AdS and the formation of the black hole is provided of the formation of a trapped surface. In the dual language, the multiplicity of the ion collision process is estimated as the area of the trapped surface. The second holographic model for quark-gluon plasma formed in the heavy ion collisions is based on AdS-Vaidya model. Within this model we estimate the thermalization time and its dependence on centricity as well as dethermalization time, related with the freeze-out time. - 13.03.2013
**Mikhail Zubkov (ITEP)***"Nambu sum rule in the NJL models: from superfluidity to top quark condensation"*ppt

Abstract:

It may appear that the recently found resonance at 125 GeV is not the only Higgs boson. We point out the possibility that the Higgs bosons appear in models of top-quark condensation, where the masses of the bosonic excitations are related to the top quark mass by the sum rule similar to the Nambu sum rule of the NJL models. This rule was originally considered by Nambu for superfluid $^3$He-B and for the BCS model of superconductivity. It relates the two masses of bosonic excitations existing in each channel of Cooper pairing to the fermion mass. An example of the Nambu partners is provided by the amplitude and the phase modes in the BCS model describing Cooper pairing in the s-wave channel. This sum rule suggests the existence of the Nambu partners for the 125 GeV Higgs boson. Their masses can be predicted by the Nambu sum rule under certain circumstances. For example, if there are only two states in the given channel, the mass of the Nambu partner is $\sim$ 325 GeV. They together satisfy the Nambu sum rule $M_1^2 + M_2^2 = 4 M_t^2$, where $M_t \sim $174 GeV is the mass of the top quark. If there are two doubly degenerated states, then the second mass is $\sim$ 210 GeV. In this case the Nambu sum rule is $2 M_1^2 + 2 M_2^2 = 4 M_t^2$. In addition, the properties of the Higgs modes in superfluid $^3$He-A, where the symmetry breaking is similar to that of the Standard Model of particle physics, suggest the existence of two electrically charged Higgs particles with masses around 245 GeV, which together also obey the Nambu sum rule $M_+^2 + M_-^2 = 4 M_t^2$.

Based on the papers: arXiv:1302.2360 by G.E.Volovik, M.A.Zubkov, and arXiv:1301.6971 by M.A.Zubkov. - 20.02.2013
**Yu. B. Ivanov (Kurchatov Institute, Moscow)***"Heavy-Ion Collisions within Multi-Fluid Simulations: Scenarios with and without Deconfinement Transition"*pdf

Abstract:

Simulations of relativistic heavy-ion collisions within the three-fluid model, employing a purely hadronic EoS and two versions of EoS involving the deconfinement transition, are presented. The latter are an EoS with a first-order phase transition and another with a smooth crossover transition. The analysis is performed in a wide range of incident energies 2.7 GeV $\le \sqrt{s_{NN}}\le$ 39 GeV in terms of the center-of-mass energy. First results of these different scenarios are compared with available experimental data. Scenarios with a deconfinement transition look preferable at high incident energies $\sqrt{s_{NN}}\ge$ 5 GeV. It is found that the predictions within deconfinement-transition scenarios exhibit a ``peak-dip-peak-dip'' irregularity (in the dependence on the incident energy) of the form of the net-proton rapidity distributions in central collisions. This irregularity signals the onset of deconfinement occurring in the hot and dense stage of the nuclear collision. - 06.02.2013
**Yuri Kalinovsky (LIT JINR)***"Pion dissociation and Levinson's theorem in hot PNJL quark matter"*pdf

Abstract:

Pion dissociation by the Mott effect in quark plasma is described within the generalized Beth-Uhlenbeck approach on the basis of the PNJL model which allows for a unified description of bound, resonant and scattering states. As a first approximation, we utilize the Breit-Wigner ansatz for the spectral function and clarify its relation to the complex mass pole solution of the pion Bethe-Salpeter equation. Application of the Levinson theorem proves that describing the pion Mott dissociation solely by means of spectral broadening of the pion bound state beyond $T_{\rm Mott}$ leaves out a significant aspect. Thus we acknowledge the importance of the continuum of scattering states and show its role for the thermodynamics of pion dissociation.

Reference: arXiv:1212.5245 - 23.01.2013
**Pavel Levashov (Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow)***"Thermodynamic and transport properties of strongly-coupled degenerate electron-ion plasma by first-principle approaches"*pdf ppt

Abstract:

An approach is assumed to be a first-principle if it doesn’t rely upon any empirical information except for fundamental physical constants. This definition covers a great number of physical models, however, not all of them gives reliable results in the case of strong interaction and degeneracy. In this presentation several methods of calculation of thermodynamic and transport properties of strongly coupled quantum plasma will be covered: path-integral Monte Carlo, Wigner dynamics, density functional theory and quantum molecular dynamics. The advantages and disadvantages of these approaches will be considered and practical examples of computations will be mentioned. In particular, the methods will be applied to electron-hole plasma of semiconductors, hydrogen and deuterium as well as to dense plasma of metals. Comparison with available experimental data will be analyzed and further perspectives of first-principle approaches for strongly-coupled plasma will be discussed. - 16.01.2013
**Aleksander Gorsky (ITEP)***"Nonperturbative defects in the dense QCD"*pdf

Abstract:

We consider two types of nonperturbative defects in the CFL phase of the dense QCD. It will be argued that there are nonabelian strings with a nontrivial worldsheet theory and monopoles localized on the string worldsheet. - 15.01.2013
**M. Müller-Preussker (Humboldt University Berlin)***"Confinement viewed with dimeron and dyon ensembles."*pdf

Abstract:

We describe two recent attempts to simulate dimeron and dyon ensembles. For zero temperature, following old confinement ideas put forward by Callan, Dashen and Gross, (anti-) dimeron configurations are Monte-Carlo sampled according to their classical action. We show that with an increasing bare coupling the dimerons become more and more dissociating pointing to a meron picture of the QCD vacuum state. Confinement is then viewed numerically in terms of an area law of Wilson loops or an approximate linearly rising potential. For non-zero temperature, guided by caloron solutions with non-trivial holonomy as invented by Kraan and van Baal a couple of years ago, we discuss ensembles of (anti-) dyon caloron constituents. Approximating them as Abelian monopoles one analytically can compute the string tension as a function of the dyon gas density and the temperature. On the other hand, simulating the monopole gas numerically one easily sees that the long-range tails of their respective fields cannot be simply treated within a finite volume. We describe that a solution of the severe finite-size problem can be found with Ewald's summation technique well-known in plasma physics. The numerical result obtained in the infinite volume limit nicely agrees with the analytical result.

References:

1) F. Bruckmann, S. Dinter, E.-M. Ilgenfritz, B. Maier, M. Muller- Preussker, M. Wagner, "Confining dyon gas with finite-volume effects under control", Phys. Rev. D85 (2012) 034502, arXiv:1111.3158 [hep-ph].

2) F. Zimmermann, H. Forkel, M. Muller-Preussker, "Vacuum structure and string tension in Yang-Mills dimeron ensembles", Phys.Rev. D86 (2012) 094005, arXiv:1202.4381 [hep-ph]. - 11.01.2013
**Florian Burger (Humboldt University Berlin)***"Critical temperature and equation of state from $N_f$ = 2 twisted mass lattice QCD"*pdf

Abstract:

I will present results of our ongoing investigation of the finite temperature QCD phase transition with two flavors of maximally twisted mass Wilson quarks. The determination of Tc from several observables is discussed and the question of the universality class of the two-flavor theory will be addressed by looking at the scaling towards the chiral limit and the magnetic equation of state. Further, I will present results for the trace anomaly, pressure and energy density. - 12.12.2012
**Tin Sulejmanpasic (University of Regensburg)***"Dyons in QCD and Chiral Symmetry Breaking"*pdf

Abstract:

SU(N) calorons with nontrivial holonomy are a natural generalization of instantons at finite temperature, which split into N objects called dyons. As still in their infancy, a proper model of the vacuum structure in terms of dyons is important to develop. I will discuss some of the implications of dyons and the effect on chiral symmetry breaking for fundamental, as well as adjoint fermions. Crucial objects for chiral symmetry breaking are fermionic zeromodes on top of the dyons. In particular, the analytic behavior of these modes is different for fundamental and adjoint fermions and will induce a different behavior for adjoint and fundamental chiral condensation, which can potentially explain the different behavior in fundamental and adjoint chiral transition observed on the lattice. - 05.12.2012
**V. O. Nesterenko (BLTP JINR)***"Vorticity in Atomic Nuclei"*pdf

Abstract:

Дается краткий обзор вихревого движения в ядрах. Обсуждаются альтернативные определения вихревого движения и их реализация в различных моделях. Даются примеры одночастичных и коллективных вихревых возбуждений. Подробно рассматривается вихревой дипольный тороидный резонанс и его связь с другими коллективными модами. - 28.11.2012
**Boris Kerbikov (ITEP)***"Quark-antiquark system in ultra-intense magnetic field"*pdf

Abstract:

We study the relativistic quark-antiquark system embedded in magnetic field (MF). The Hamiltonian contains confinement,color Coulomb and spin-spin interactions. We analytically follow the evolution of the spectrum as a function of MF. In the large Nc limit the mass of the ground state becomes negative for MF above the critical value. The results are compared with recent lattice calculations. - 21.11.2012
**S. V. Molodtsov (BLTP JINR)***" Four-fermion interaction in the context of study of relativistic heavy ion collisions" (in Russian)*pdf

*"Четырехфермионное взаимодействие в контексте изучения соударений релятивистских тяжелых ионов"*

Г. М. Зиновьев, С. В. Молодцов

Abstract:

Почти идеальная жидкость, обнаруженная в экспериментах по столкновениям ультрарелятивистских тяжелых ионов, исследуется с использованием кварковых ансамблей с четырехфермионным взаимодействием в качестве основополагающего теоретического приближения. При этом проводится сравнительный анализ возникающих моделей квантовых жидкостей и отмечается, что характерным их свойством является наличие фазового перехода газ-жидкость. Обсуждается проблема неустойчивости капель кварковой жидкости с малым числом кварков, связанная с возможным формированием кирального солитона. Исследуется смешанная фаза вакуума и барионной материи, как возможный сценарий ее стабильности. Рассматриваются некоторые аспекты цветовой сверхпроводимости. Изучается широко обсуждаемое в последнее время нетривиальное термодинамическое состояние - фермионный конденсат. На примере модельной задачи анализируется неожиданная возможность связи между затравочной и эффективной константами взаимодействия. Отмечено, что простая вычитательная процедура может приводить к конечному результату без типичной логарифмической сингулярности для наблюдаемой константы связи, как функции передаваемой энергии. - 19.09.2012
**Anton Kononenko (JINR)***"Magnetic scenario of Quark Gluon Plasma. New lattice results in QCD and SU(3) gluodynamics"*

Abstract:

New results of our ongoing lattice study aiming to support the magnetic scenario of the quark-gluon plasma (QGP) will be presented. To be concise, the magnetic scenario provides arguments that magnetic degrees of freedom are responsible for the QGP's liquid properties. On a lattice, these degrees of freedom can be associated with magnetic monopoles obtained in the Maximal Abelian Gauge. I will present numerical results obtained in lattice SU(3) gluodynamics on one hand and lattice QCD on the other. I will cover such topics as: monopole density; dependence of the magnetic coupling and the magnetic mass on the temperature. I will also consider several characteristics of the monopole clusters in the confinement phase aiming at better understanding of the quantum fluctuations responsible for confinement in SU(3) gluodynamics and QCD. - 27.07.2012
**Michael Buballa (Technische Universitaet Darmstadt, Institut fuer Kernphysik)***"Inhomogeneous phases in the QCD phase diagram"*pdf

Abstract:

Most studies of the QCD phase diagram tacitly assume that the different phases are homogeneous in space. However, there are good arguments that inhomogeneous phases could also be present. In this talk we focus on inhomogeneous chirally symmetry breaking phases, where the quark condensate varies in space. Model calculations suggest that the first-order chiral phase transition, including the critical endpoint, could be removed from the phase diagram when inhomogeneous phases are included. The mechanisms which lead to these solutions are discussed and physical interpretations are given. Inhomogeneous color superconducting phases are briefly discussed as well. - 18.07.2012
**V. G. Bornyakov (IHEP and ITEP)***"Color-magnetic monopoles in lattice QCD at finite temperature: Most recent results"*pdf

Abstract:

Thermal monopoles have been found to be important field configurations in gluodynamics describing the gluon plasma close to the transition. We present here results of a first study of thermal monopoles in non-quenched lattice QCD with two flavors of dynamical quarks to describe the quark-gluon plasma. The density of monopoles and the parameters of their interaction are computed both at high temperature and near to the transition. A comparison with the thermal monopoles observed in gluodynamics is made.

References:

arXiv:1111.0169 (by V. G. Bornyakov and A. G. Kononenko), see also: arXiv:1110.6308 and arXiv:1104.1063 - 13.06.2012
**Andrey Sadofyev (ITEP)***"Chiral effects in superfluid"*pdf

Abstract:

Recently, there were intense studies of hydrodynamics of chiral liquids. A crucial novel point is existence of new transport coefficients, overlooked in the text-book approaches. The coefficients are considered to be completely fixed by the coefficient in front of the chiral anomaly. This result could be obtained in a lot of approaches. Despite of variety of the assumptions tried, all these approaches treat the liquid as a single-component. We will consider here the system where the single-component assumption is not valid and discuss which physical picture is more justified. - 06.06.2012
**A. Leonidov (Lebedev Institute of Physics, RAS, Moscow)***"Turbulent nonabelian matter in high energy nuclear collisions"*pdf

Abstract:

Dense non-abelian matter created in ultrarelativistic heavy ion collisions undergoes several stages of evolution, from initially produced glasma through quark-gluon plasma to formation of final hadrons. In the recent years there accumulated significant theoretical evidence for the presence of instabilities and resulting stochastic tubulent-like state of glasma and quark-gluon plasma. In the talk a review of these issues is given. - 05.06.2012
**Sunyoung Shin (BLTP JINR)***"A dual geometry of the hadron in dense matter by Bum-Hoon Lee, Chanyong Park, Sang-Jin Sin published in JHEP 0907 (2009) 087 "*pdf

Abstract:

This article discusses the dual geometries of confinement/deconfinement in the hard wall model. Thermal charged AdS, which is the zero mass limit of the Reissner-Nordstrom AdS black hole, is proposed as the dual geometry corresponding to confining phase of QCD. We briefly review gauge/gravity duality, hard wall model and Hawking-Page transition, and go through the article. Below find the abstract of the article JHEP 0907 (2009) 087 : We identify the dual geometry of the hadron phase of dense nuclear matter and investigate the confinement/deconfinement phase transition. We suggest that the low temperature phase of the RN black hole with the full backreaction of the bulk gauge field is described by the zero mass limit of the RN black hole with hard wall. We calculated the density dependence of critical temperature and found that the phase diagram closes. We also study the density dependence of the $\rho$ meson mass. - 30.05.2012
**V.V. Braguta (ITEP)***"Electromagnetic superconductivity of vacuum induced by strong magnetic field: numerical evidence in lattice gauge theory"*pdf

Abstract:

Using numerical simulations of SU(2) gauge theory we demonstrate that an external magnetic field leads to spontaneous generation of quark condensates with quantum numbers of electrically charged $\rho$ mesons if the strength of the magnetic field exceeds the critical value $e B_c = 0.927(77) GeV^2$ or $B_c =(1.56 \pm 0.13)* 10^16 Tesla$. The condensation of the charged $\rho$ mesons in strong magnetic field is a key feature of the magnetic-field-induced electromagnetic superconductivity of the vacuum. - 18.05.2012
**D. Blaschke (BLTP JINR and University Wroclaw, Poland)***"A Microscopic Approach to Chemical Freeze-out in Heavy-Ion Collisions"*pdf

Abstract:

The derivation of a formula for the chiral condensate in a hadron resonance gas is presented. A model for chemical freeze-out is presented where the melting of the chiral condensate in hot, dense hadronic matter leads to an increase in the hadronic radii facilitating fast chemical equilibration. The model predictions are in agreement with recent results from the beam energy scan program of the STAR experiment at RHIC Brookhaven. - 2.05.2012
**M.Tokarev (LHEP JINR)***"z-Scaling & The Search for Signatures of a Phase Transition and a Critical Point in Heavy Ion Collisions"*pdf

Abstract:

The method of data analysis (z-scaling approach) based on self-similarity and locality of constituent interactions in hadron and nucleus collisions at high energy is briefly described. It is applied for the analysis of BES data in order to search for signatures of a phase transition and a Critical Point. Some results of the analysis of inclusive hadron spectra measured in heavy ion collisions at RHIC over a wide range of the energies √s_NN = 7.7-200 GeV are presented. The microscopic scenario of constituent interactions in the framework of this approach is discussed. The dependence of the energy loss on the momentum of the produced hadron, the energy and centrality of the collision is studied. The self-similarity of the constituent interactions in terms of momentum fractions is used to characterize the nuclear medium by a particular ``specific heat'' and the colliding nuclei by fractal dimensions. Kinematical regions which are assumed to be the most preferable ones to search for signatures of a phase transition of nuclear matter are discussed. The discontinuity of the ``specific heat'' is assumed to be a signature of crossing a phase transition or passing the Critical Point. - 25.04.2012
**B. V. Martemyanov (ITEP)***"Topological objects across the phase transition as seen by the cooling method in SU(3) gluodynamics and in QCD with two flavors"*

Abstract:

Topological objects are studied using the cooling method of lattice fields representing SU(3) gluodynamics on one hand and Quantum Chromodynamics with N_f=2 quark flavors on the other. We compare the probabilities to find topological non-trivial, in particular selfdual and antiselfdual configurations in the cooling histories of Monte Carlo lattice configurations, that have been generated close to the transition region in the two phases, confinement and deconfinement. In SU(3) gluodynamics (N_f=0) this probability drops sharply at the temperature of the first order phase transition, while the analytic crossover of full QCD from confinement to deconfinement is accompanied by a smooth decrease of this probability. The topological susceptibilities obtained by this analysis behave in a similar way. The temperature behaviour of the latter is compared with and found to be close to the temperature behaviour of the topological susceptibilities determined by other methods. - 18.04.2012
**V. S. Filinov (Joint Institute for High Temperatures of RAS, Moscow)***"Quantum Simulation of Thermodynamic and Transport Properties of the Quark-Gluon Plasma"*pdf

Abstract:

For quantum simulations of thermodynamic and transport properties of the quark-gluon plasma (QGP) within a unified approach we combine Path Integral and Wigner (phase space) formulations of quantum mechanics. Thermodynamic properties of a strongly coupled QGP of constituent quasiparticles are studied by means of color path integral Monte-Carlo simulations (CPIMC). For the purpose of simulations we have presented the QGP partition function in the form of a color path integral with a new relativistic measure instead of the usual Gaussian one used in Feynman and Wiener path integrals. For the integration over the color degree of freedom we have developed a sampling procedure according to the SU(3) Haar measure. It is shown that this method is able to reproduce the available Lattice Quantum Chromodynamics (LQCD) data describing the deconfined phase. Canonically averaged two-time quantum operator correlation functions and related kinetic coefficients have been calculated according to Kubo formulae. In our approach, CPIMC is used not only for the calculation of thermodynamic functions, but also to provide equilibrium initial conditions (i.e. specific coordinates, momenta, spin, flavor and color of multi-quasiparticle configurations) in order to accomplish the generation of color-phase-space trajectories as solutions of dynamic differential equations. Correlation functions and kinetic coefficients are calculated as averages of suitable Weyl's symbols of dynamic operators along these trajectories. Using this approach we have calculated the diffusion coefficient and the shear viscosity in good agreement with experimental data obtained at RHIC. These results are obtained in collaboration with Yu. B. Ivanov (Kurchatov Institute Moscow and GSI Darmstadt, Germany), M. Bonitz (University Kiel, Germany), V. E. Fortov and P. R. Levashov (both JIHT, RAS, Moscow). - 11.04.2012
**M.Tokarev (LHEP JINR)***"Beam Energy Scan at RHIC & Search for Signatures of Phase Transition and Critical Point in z-scaling approach"*pdf

Abstract:

The Beam Energy Scan program in AuAu collisions performed at RHIC is reviewed. The main goal of the program is the search for clear signatures of phase transition of nuclear matter and the location of a possible Critical Point. Experimental data on particle (π,K,p,φ,Λ,Ξ,Ω,…) and antiparticle yields allow to study collective phenomena as a direct and elliptic flow, nuclear modification factors, transverse momentum spectra, fluctuations of transverse momentum, particle ratios, net-baryon number and correlations of different quantities (Δφ-Δη) and their dependence on energy and centrality collisions. Results (temperature, chemical potential,..) of data analysis in framework of some theoretical models are discussed. Method of data analysis (z-scaling approach) based on self-similarity and locality of constituent interactions in hadron and nucleus collisions at high energy is described. It is applied for analysis of BES data for search for signatures of phase transition and Critical Point. Some results of analysis of inclusive hadron spectra measured in heavy ion collisions at RHIC over a wide range of the energy √sNN = 7.7-200 GeV are presented. Microscopic scenario of constituent interactions in the framework of this approach is discussed. Dependence of the energy loss on the momentum of the produced hadron, energy and centrality of the collision is studied. Self-similarity of the constituent interactions in terms of momentum fractions is used to characterize the nuclear medium by a "specific heat" and the colliding nuclei by fractal dimensions. Kinematical regions which is assumed to be of most preferable for search for signatures of phase transition of nuclear matter produced in HIC in BES are discussed. Discontinuity of a "specific heat" is assumed to be a signature of phase transition and a Critical Point. - 21.03.2012
**O. V. Rogachevsky (VBLHEP JINR)***"Event structure of multiparticle production in nucleus-nucleus collisions"*pdf

Abstract:

The configurations of multiparticle events observed in the nucleus-nucleus collisions are considered in the transverse momentum phase space. The appearance of some features in the inclusive particle spectra may be traced back to the different event structures. Event structure also could have an impact on the some effects (flow, jet suppression, ridge), observed recently in nucleus-nucleus collisions at RHIC and LHC. - 11.03.2012
**Nikolai Kochelev (BLTP JINR)***"The Quark Anomalous Chromomagnetic Moment Induced by the QCD Vacuum, a New Model for Pomeron and Odderon, and the Nonperturbative Quark Energy Loss in Quark-Gluon Matter"*

Abstract:

It is shown that the existence of strong vacuum gluon fields called instantons in nonperturbative QCD vacuum leads to appearance of a large anomalous quark chromomagnetic moment (AQCM). We suggest a new model for Pomeron and Odderon exchanges based on the AQCM and discuss the dynamics of exclusive high energy hadron-hadron scattering at large momentum transfer. We show that there is the nonfactorizable contribution to the inclusive cross section for hadron production at high energy which gives also the rise to single-spin asymmetries for meson production observed in the many reactions. The possible important role of AQCM contribution to the fast parton energy loss in cold and hot quark-gluon matter is under discussion. - 29.02.2012
**J. Pawlowski (University of Heidelberg)***"On the thermodynamics and phase structure of QCD"*pdf

Abstract:

I review the progress made in recent years with functional continuum methods in our understanding of the QCD phase diagram. Within this approach QCD correlation functions of quarks, gluon and hadrons are computed non-perturbatively from first principles. The approach has been used complementary as well as in combination with lattice computations, a particular strength being its applicability to the chiral limit and at finite density. In the past decades this has led to a plethora of quantitative as well as qualitative results for the hadronic mass spectrum, the confinement-deconfinement and the chiral phase transition, the role of fluctuations (non-Gaussianities) and the dynamics of QCD far from equilibrium. In the present talk I will mainly concentrate on the phase structure of QCD at vanishing and finite temperature and density, including the effects of strong (chromo-) magnetic and electric fields such as present in heavy ion collisions. Specifically results are discussed for the order parameters of confinement-deconfinement and chiral phase transitions, the nature of these transitions and their interrelation, as well as the thermodynamics of QCD. The talk concludes with a discussion of the further prospects for our understanding of the phase structure of QCD. - 15.02.2012
**A.G. Litvinenko (LHEP JINR)***"Review of some results of heavy ion collisions. Continuation."*ppt

Abstract:

In the second part of the talk, experimental results are discussed that contain more specific information about the properties of the excited hadronic matter. In particular, some properties of the elliptic flow (scaling in the number of valence quarks, the elliptic flows of heavy quarks) are presented. Besides this, the effect of melting of resonances and other effects and observables, associated with the very early stage of the collision between heavy ions, are pointed out. This concerns the effect of jet quenching and the direct photon spectra. - 08.02.2012
**A.A. Petrukhin (MEPhI)***"Cosmic rays of very high energies (> 10^15 eV) and quark-gluon matter"*ppt

*"Космические лучи сверхвысоких энергий (> 10^15 эВ) и кварк-глюонная материя"*

Abstract:

В экспериментах, проведенных в космических лучах при энергиях выше $ 10^{15}$ эВ ($>1$ ТэВ в системе центра масс), зарегистрированы необычные события разного типа, которые не находят своего объяснения в рамках существующих моделей адронного взаимодействия, основанных на экстраполяции ускорительных данных. Для их объяснения было предложено много различных идей и моделей, но ни одна из них не позволяет описать с единой точки зрения всю совокупность имеющихся экспериментальных данных. В докладе рассматривается модель образования кварк-глюонной материи в ядро-ядерных взаимодействиях, которая позволяет непротиворечивым образом описать имеющиеся экспериментальные результаты, полученные в космических лучах сверхвысоких энергий. Обсуждаются возможности проверки нового подхода в экспериментах на LHC. - 01.02.2012
**A.G. Litvinenko (LHEP JINR)***"Review of some results of heavy ion collisions"*ppt

Abstract:

Observables and basic definitions used to describe nucleus-nucleus collisions are discussed. The main results obtained at RHIC are considered in the review. Where it is possible a comparison with results obtained at other energies is made. - 25.01.2012
**V.D. Toneev (BLTP JINR)***"Evolution of electromagnetic field in heavy ion collisions and chiral magnetic effect"*ppt

*"Эволюция электромагнитного поля в столкновении тяжелых ионов и киральный магнитный эффект"*

Abstract:

Кинетическая модель динамики адронных струн обобщена на случай формирования и эволюции электромагнитного поля с учетом влияния этих электрических и магнитных полей на распространение квазичастиц в ядерной среде. Для периферических Au+Au(200 ГэВ) столкновений детально проанализирована пространственно-временная структура полей и дана оценка достигаемых значений поля. Показано, что хотя значения электрических и магнитных полей велики, они практически не влияют на наблюдаемые величины (в том числе и на эффект разделения зарядов относительно плоскости реакции) из-за взаимной компенсации действия этих полей на транспорт квазичастц. Выполнен анализ недавних экспериментов RHIC по поиску кирального магнитного эффекта при умеренных энергиях. Результаты RHIC при энергиях столкновения 7.7 и 11.5 ГэВ могут быть разумно объяснены в рамках адронной модели. - 18.01.2012
**Michael Mueller-Preussker (Humboldt-University Berlin)***"Two-colour lattice QCD at T>0 in the presence of a strong magnetic field"*pdf

Abstract:

We present a lattice calculation for hadronic or quark-gluon matter at non-zero temperature under the influence of a strong magnetic field. We restrict ourselves to SU(2) gauge fields and four degenerate dynamical quark flavours each having the same electric charge. We employ the staggered formulation for the fermionic lattice fields and compute numerically the Polyakov loop and the chiral condensate as well as their susceptibilities in order to establish the dependence of the critical temperature on the external magnetic field. In detail we discuss the enhancement of chiral symmetry breaking in the chirally broken phase as well as its restoration in the deconfined phase. - 11.01.2012
**V.V. Braguta (ITEP)***"Abelian Monopoles and Properties of Quark-gluon Plasma"*pdf

*"Абелевые монополи и свойства кварк-глюонной плазмы"*

Abstract:

Одной из моделей, которая предлагает объяснение конфайнмента является модель вакуума КХД как дуального сверхпроводника. В этой моделе считается что в вакууме КХД в конденсированном состоянии присутствуют хромомагнитные монополи. При моделировании вакуума КХД в вычислениях на решетке роль хромомагнитных монополей играют монополи в максимально абелевой калибровке. Так, известно, что переход конфайнмент-деконфайнмент однозначно связан с появлением-исчезновением конденсата таких монополей. Недавние теоретические исследования кварк-глюонной плазмы показали, что монополи могут играть важную роль в таких свойствах плазмы как сверхтекучесть, которая была обнаружена на эксперименте RHIC. Из этого можно сделать вывод, что, изучая свойства абелевых монополей, мы изучаем свойства полевых конфигураций ответственных не только за конфайнмент, но и за коллективные явления в кварк-глюонной плазме. В докладе будут представлены новые результаты изучения абелевых монополей в кварк-глюонной плазме в рамках решеточной SU(2) КХД. В частности, в докладе планируется обсудить взаимодействие монополей, плотность, размер монополей, масса монополей, влияние монополей на свойства кварк-глюонной плазмы и т. д. Помимо этого, будут представлены результаты доказывающие, что монополи являются не только частицами, которые несут хромомагнитный заряд, но и частицами несущими хромоэлектрический заряд и в пределах ошибки вычислений эти заряды равны между собой. - 7.12.2011
**Leonard Fister (University Heidelberg, Germany)***"Yang-Mills Theory at Non-Vanishing Temperature"*pdf

Abstract:

We study the temperature dependence of correlators in Yang-Mills theory. For this purpose we utilise a purely thermal renormalisation group flow equation, and obtain the full thermal propagators. Interestingly, the electric screening mass is sensitive to the confinement-deconfinement phase transition. We also compute thermodynamic quantities such as the pressure. - 30.11.2011
**B. V. Martemyanov (ITEP)***Dilepton production in elementary processes and in heavy ion collisions at intermediate energies*pdf

*"Рождение дилептонов в элементарных реакциях и столкновениях ионов при промежуточных энергиях"*

Abstract:

Предлагается единое описание рождения векторных мезонов и дилептонов в элементарных процессах и столкновениях тяжёлых ионов. Это означает, что все дилептоны появляются через промежуточные векторные бозоны. Рождение векторных мезонов предполагается результатом возбуждения нуклонных резонансов. Соответствующая модель доминантности векторных мезонов расширяется с целью описания переходных электромагнитных формфакторов резонансов. В случае столкновения тяжёлых ионов обсуждаются эффекты ядерной среды. - 16.11.2011
**P.V. Buividovich (ITEP)***"Nonrelativistic and Relativistic Hydrodynamics on the Lattice"*

Abstract:

Lattice discretization of kinetic Boltzmann equation is one of efficient ways for numerical simulations in viscous nonrelativistic hydrodynamics, which allows to consider turbulence, convection and other non-equilibrium processes. We consider the derivation of macroscopic hydrodynamical equations from continuum Boltzmann equation and from its lattice discretization. It turns out that numerical solution of Boltzmann equation on the lattice is simpler than the solution of the corresponding Navier-Stokes equation. We also consider the generalization of this approach to relativistic theory, in particular, to the simulations of quark-gluon plasma.