In the first part of the talk I discuss the basic aspects of the light-cone path integral (LCPI) approach to the radiative energy loss and LPM effect in QED and QCD. I will show the comparison of the theoretical predictions with the SLAC and CERN SPS data on the LPM effect in photon bremsstrahlung from high energy electrons. In the second part of the talk I will discuss application of the LCPI method to the induced gluon emission in a hot quark-gluon plasma and to the jet quenching phenomenon in AA-collisions at RHIC-LHC energies.

In the wake of exploring uncertainty in the full angular distribution of the $B\to K\pi+\mu^+\mu^-$ caused by the presence of the intermediate scalar $K^\ast_0$ meson, we perform the straightforward calculation of the $B(B_s)\to S$ ($S$ is a scalar meson) transition form factors in the full kinematical region within the covariant quark model. We restrict ourselves by the scalar mesons below 1 GeV: $a_0(980)$, $f_0(500)$, $f_0(980)$, $K^\ast_0(800)$. As an application of the obtained results we calculate the widths of the semileptonic and rare decays $B(B_s)\to S\ell\bar\nu$, $B(B_s)\to S\ell\bar\ell$ and $B(B_s)\to S\nu\bar\nu$. We compare our results with those obtained in other approaches.

The fact that nuclei have diffuse surfaces (rather than being simple spheres) has dramatic consequences on the interpretation of various nuclear experimental data, for example, the RHIC heavy-ion data. At present, the nuclei are used for the study of hadron properties and their interaction at different nuclear density (in the center and in the peripheral domain of nucleus). This topics provide a connection between experiments with proton beams, lepton beams, and high energy heavy ion collisions.

$K^{+}$-meson at intermediate energy can probe the whole volume of nuclei owing to their small cross section of interaction with nucleons. We show that new experimental data on the total cross section of $K^{+}$-nuclei interaction cannot be described by the novel well-elaborated Glauber Monte Carlo model. (Widely utilized in heavy-ion collisions, probing hot and dense hadronic matter.)

At the same time, in the case of projectiles (e.g., K${}^{-}$ meson or protons) interacting in the peripheral region of the nuclei (with small density), the agreement of our calculated cross sections with data is rather good. This may indicate on a unique event, in-medium effect, in the region of the nucleus with high density.

We give a short overview of the motivation and discuss results of the approach to QCD vacuum as a medium describable in terms of statistical ensemble of almost everywhere covariantly constant Abelian (anti-)self-dual gluon fields which also can be seen as a random ensemble of domain wall networks. The domain walls separate the space-time regions with Abelian self-dual and anti-self-dual fields. The network of the domain walls is introduced as a combination of multiplicative and additive superposition of kinks.

A relativistic quantum field theoretical description of mesons based on the domain model of QCD vacuum is reviewed. In this approach the mesons appear as colorless collective excitations in the confining QCD vacuum. New results for the masses and leptonic decay constants of radially excited mesons are presented. The radial excitations of light, heavy-light mesons and heavy quarkonia are described analytically from a single point of view. The model has a minimal for QCD set of parameters: quark masses, strong coupling constant, gluon condensate <$g^2F^2$> and the mean domain size related to the topological susceptibility of pure gluodynamics.

Electromagnetic FFs are fundamental quantities, which describe the internal structure of hadrons and the dynamic properties of their charge and magnetic distributions. Although experiments and theories have started to develop since decades, recently the opening of new experimental possibilities has driven an intensive and renewed activity in the field. The precise data which have been obtained from polarized electron-proton scattering, mostly at Jefferson Laboratory, have shown that the behavior of the electric and magnetic distributions inside the proton is different, and that the electric FF does not follow a dipole distribution becoming eventually negative at large momentum transfer. At electron-positron facilities, FFs have been measured in a wide time-like kinematical region using initial state radiation at SLAC (BABAR) and the BES collaboration will measure very precisely proton and neutron FFs in the threshold region. In next future an antiproton beam with momentum up to 15 GeV/c will be available at FAIR (Darmstadt). Measurements by the PANDA collaboration will allow firstly the individual measurement of electric and magnetic FFs in the time-like region at relatively high momentum transfer.

This will drive the effort forward a global description of FFs in the full kinematical region. We will show the global trend of the data in space and time-like regions and illustrate on selected examples the present understanding and the open problems.