Gabor J. Kalman

On 10 December 2022 the plasma and many-body theoretical physics communities lost a distinguished and much-respected member, Gabor J. Kalman, following a protracted illness.

Gabor, as he was known to us, was born in Budapest, Hungary, on 12 December 1929. He obtained an electrical engineering degree from the Budapest University of Technology and in 1952 started working at the atomic physics department of the Central Research Institute for Physics. After the 1956 revolution, he left Hungary together with his wife and his young daughter and moved to Israel, where his son was born. He obtained his doctorate at the Technion (Israel Institute of Technology) under the supervision of Nathan Rosen. Later he became a professor at the Université de Paris (Orsay, France) and then in 1970 a collaborator and professor at the physics department of Boston College.

He was one of the initiators of the research on strongly coupled coulomb systems and one of the founders of the SCCS conference series on this topic. His research was motivated by the desire for an understanding of the response functions and collective excitations of strongly coupled (classical and quantum) many-particle systems in the nonperturbative regime.

Together with Ken Golden, Gabor developed the quasilocalized charge approximation (QLCA) theoretical method, which allows the determination of the dispersion relations of collective modes in many-particle systems, given the knowledge of the static characteristics (pair correlation function) of the systems. The QLCA method is essentially unique for the description of electrically charged liquid-state systems and bridges the gap between the two well-understood phases: the weakly coupled state (describable by perturbative methods) and the crystalline state (characterizable by phonons). Gabor and his collaborators successfully applied the QLCA method for the determination of the dispersion relations of collective excitations in one- and two-component plasmas, in 2D electron systems, double and multilayers of charged particles, and dusty plasmas. The QLCA theory showed that in double layers, the counterphase oscillations generate an optical mode. The QLCA theory also predicted the existence of correlation-maintained shear collective excitations in the liquid state and the emergence of a magnetic shear mode in the presence of a magnetic field. In addition, Gabor did pioneering work in the study of the quadratic response functions of many-particle systems, the nonlinear fluctuation-dissipation theory, the mechanism of electrical screening of contaminant ions in plasmas, the physics of instabilities, and the broadening of spectral lines.

Beginning in 1970 Gabor conducted research and gave lectures at numerous universities and research institutes as an invited or honorary member: Harvard (honorary associate); University of Oxford (senior scholar); Observatoire de Meudon and Universite de Orleans, France (professeur d’echange); Soreq Research Institute, Israel (senior researcher); and University of California, San Diego (scholar of the university). He had close collaborations with research groups at the Massachusetts Geophysical Laboratory (USAF Geophysics Laboratories), UC San Diego, and the Solid State Physics Research Institute of the Hungarian Academy of Sciences (now Wigner RCP).

He was an outstanding teacher of several generations of university students and the supervisor of more than 30 PhD theses. He was a fellow of the American Physical Society and the New York Academy of Sciences and an external member of the Hungarian Academy of Sciences. Until his last days, he was actively researching and publishing in leading journals.

Gabor J. Kalman leaves a legacy of deep and elegant papers covering response functions and collective excitations in both classical and quantum strong-coupled many-particle systems. His most recognized publications introduce the principles of the QCLA method and its application to strongly coupled dusty plasmas , which he shared with one of his closest collaborators (Golden) and his early PhD student and longtime collaborator (Marlene Rosenberg).

Gabor is survived by his children Katalin and Ron. We miss him dearly.

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