Dirk ter Haar (Apr. 22, 1919 - Sept. 3, 2002) was an outstanding Dutch theoretical physicist, best known for his works in statistical physics and quantum mechanics, astrophysics, solid state physics and foundations of statistical mechanics.

Dirk ter Haar studied physics at Leiden University. His teacher and mentor was Hendrik A. Kramers. The PhD. thesis of Dirk ter Haar had the title "Studies on the Origin of the Solar System" (1948). The ideas developed in the thesis still influence the modern researchers. Then for some time he was a research fellow at the Niels Bohr Institute at Kopenhagen. He visited also the Universities Purdue and Indiana in US.

In 1949 he took position reader in physics at the St.Andrews University in Scotland. In the 1950 , Dirk ter Haar emigrated to England, where he naturalized. During rest of his life Dirk ter Haar worked at Magdalen College at the Oxford University (Lecturer in Theoretical Physics 1956–9, Reader 1959–86, Fellow and Tutor in Physics 1959–86, Emeritus Fellow 1986–2002). He educated many first rank scientists, between them Anthony Leggett, who received the Nobel Prize for physics 2003.

Leggett later reminded his postgraduate research in physics at Oxford: "One person who was willing to overlook my unorthodox credentials was Dirk ter Haar, then a reader in theoretical physics and a fellow of Magdalen College, Oxford; so he signed up for research under his supervision. As with all Haar's students in that period, the tentatively assigned thesis topic was "Some Problems in the Theory of Many-Body Systems," which left a considerable degree of latitude".
Dirk ter Haar supervisory style was somewhat unusual. He took a great interest in the personal welfare of his students and their families, and was meticulous in making sure they received adequate support; indeed, he encouraged Leggett to apply for a Prize Fellowship at Magdalen, Oxford University. In the end Leggett's thesis work consisted of studies of two somewhat disconnected problems in the general area of liquid helium, one on higher-order phonon interaction processes in superfluid 4He and the other on the properties of dilute solutions of 4He in normal liquid 3He (a system which unfortunately turned out to be much less experimentally accessible than the other side of the phase diagram, dilute solutions of 3He in 4He).

Dirk ter Haar served for many years as Editor of the PHYSICS LETTERS A.

Dirk ter Haar was one of the first theoretician at the West who evaluated and started to apply the work of
N. N. BOGOLIUBOV and S. V. TYABLIKOV:
"Retarded and Advanced Green's Functions in Statistical Physics",
Dokl. Acad. Nauk SSSR, 126 (1) (1959) pp.53-56 (Sov. Phys.-Doklady 4 (1959) 589 ).
Many of his PhD students ( B. G. S. Doman, W. E. Parry, C. J. Pethick, A. Hewson, A. Leggett, etc.) used this method in their thesis.
He applied successfully that method to various problems of the quantum solid state physics, quantum theory of magnetism and quantum statistical mechanics of many particle systems.
He was translator of the book:
S. V. TYABLIKOV and V. L. Bonch-Bruevich, The Green Function Method in Statistical Mechanics, North-Holland, 1962.
and the review article:
D. N. ZUBAREV, "Double-time Green Functions in Statistical Physics", Usp. Fiz. Nauk, 71 (1960) pp.71-116 ( Sov. Phys. Uspekhi, 3 (1960) pp.320-45). This paper was reviewed in the CITATION CLASSIC.
He translated also the book A. S. Davydov, "Quantum Mechanics" and Collected Papers of L. D. Landau.

In 1984 the book dedicated to Dirk ter Haar appeared: Essays in Theoretical Physics: in honour of Dirk ter Haar. Edited by W. E. Parry. Published by Pergamon Press, Oxford, UK, 1984.

Dirk ter Haar had a gift to teach and to write. He produced many readable, clear and excellent texts which are the masterpieces of the scientific writing. His numerous review articles are very informative and helpful till now, e.g.,
D. ter Haar, Foundations of statistical mechanics. Rev. Mod. Phys. v.27, p.289 (1955).
D. ter Haar, Theory and Applications of the Density Matrix, Rep. Prog. Phys. v. 24, p.304 (1961).

Dirk ter Haar published numerous books; the best known is "Elements of Statistical Mechanics".

List of books :
* D.ter Haar, Elements of Statistical Mechanics. London: Constable (1954). 2ed (1966) New York: Holt, Rinehart & Winston; 3ed (1995) Oxford: Butterworth-Heinemann
* D. ter Haar and H. Wergeland, Elements of Thermodynamics, Addison-Wesley, 1960
* D.ter Haar, Elements of Hamiltonian Mechanics, Pergamon Press, Oxford.
* D.ter Haar, The Old Quantum Theory, Pergamon Press, Oxford, 1967.
* D.ter Haar, Lectures on Selected Topics in Statistical Mechanics, Pergamon Press, Oxford, 1977.
* D. ter Haar, Master of Modern Physics. The Scientific Contributions of H. A. Kramers, Princeton Uni. Press, 1998.

There are only a few places where the biography of Dirk ter Haar can be found.

Wikipedia electronic Encyclopedia(http://nl.wikipedia.org/) , an article DIRK TER HAAR.

PHYSICS TODAY v. 57 N 2 (2004) pp.79-80 obituary note: DIRK TER HAAR

Obituary note Dirk ter Haar, written by N. G. van KAMPEN.