Matveevich Eliashberg, has turned 90. G M Eliashberg was born on July 26, 1930 in Leningrad. In 1947, he entered the Physical Faculty of Leningrad University and graduated with honors in 1952. Five years later, he worked at the Leningrad plant Krasny Khimik (Red Chemist), where he had been assigned on graduating from university. In 1959, GM Eliashberg entered the postgraduate course of the Physical-Technical Institute in Leningrad. That same year, he published a paper formulating the theory of the superconducting state occurring owing to electron±electron interaction through the crystal lattice oscillations. In this study, he wonderfully combined the J Bardeen, L Cooper, J Schrieffer theory of superconductivity that had appeared two years before, the field theoretical formulation of this theory developed at that time by Lev Gor'kov, and A B Migdal's theory of electron±phonon interaction in normal metals. Being the basis of the microscopic description of superconductivity, the Eliashberg theory became with time a well-developed part of modern condensed state physics. Different modifications of this theory are being actively examined in application to new classes of superconductors and other mechanisms of electron±electron attraction. The remarkable recent discovery of lithium hydride superconductivity at a temperature of 250 K and a pressure of several megabars is only one of the examples of such examinations. In 1961, GMEliashberg became a junior research worker at the Physical-Technical Institute. There, he carried out a number of studies of transport phenomena in Fermi liquid. He developed the technique of analytical continuation that allowed finding frequency dependences of kinetic quantities calculated using the temperature diagram technique. This approach is conventional and is invariably used in theoretical studies, sometimes even without mentioning the name of its author. After defending his candidate thesis in 1963, GM Eliashberg left Leningrad for Chernogolovka, where he began working at the theoretical department of a branch of the Institute of Chemical Physics and then from 1965 at the newly founded Institute of Theoretical Physics (now Landau Institute for Theoretical Physics), where he has been working till the present day. In 1972, G M Eliashberg became Doctor of Physical and Mathematical Sciences, and in 1990 he was elected a corresponding member and in 2000 a full member of the Russian Academy of Sciences. In Chernogolovka, GMEliashberg taught at theMoscow Institute of Physics and Technology, first at the chair of theoretical physics in Dolgoprudnyi and then at the chair of problems of theoretical physics at the Landau Institute. The educational process is always closely related to the teacher's personality. The scientific style of Eliashberg is known for a skillful mastery of complicated analytical methods remarkably combined with a precision of the physical statement of the problem. Intercourse with G M Eliashberg gave students not only facts and knowledge, but also scientific culture, while inculcating good manners and teaching lucidity of mind. B Ivlev, L Levitov, Yu Nazarov, and others are among his disciples. When at Chernogolovka, G M Eliashberg carried out a number of studies that remained significant for many years after. In 1965, he and L P Gor'kov formulated the theory of small metallic particles. Describing an ensemble of such particles with the Wigner±Dyson distribution, the authors arrived at a number of conclusions accessible for experimental verification and anticipating the results of mesoscopyÐ the contemporary theory of quantum properties of disordered metals. In the late 1960s ± early 1970s, G M Eliashberg together with L P Gor'kov developed a consistent theory of superconducting state kinetics and derived a nonstationary generalization of the Ginzburg±Landau equations. One of the most remarkable phenomena established by him here was the amplification of superconductivity by a high-frequency field. This work by G M Eliashberg made an impact on extensive Uspekhi Fizicheskikh Nauk 190 (9) 1007 ± 1008 (2020) Translated by M V Tsaplina PERSONALIA PACS number: 01.60.+q

Mathematical Sciences, and author of numerous reviews in Uspekhi Fizicheskikh Nauk (UFN) [Physics±Uspekhi] journal, Moisei IsaakovichKaganov, passed away onAugust 31, 2019 at the age of 98. Moisei Isaakovich became famous for his brilliant work on the physics of metals and dielectrics and the physics of magnetic phenomena. His scientific style was characterized by a broad view of the subject under study, an original approach to problems, and an independent way of thinking. Moisei Isaakovich will also remain in our memory as a remarkable popularizer of science. In his popular scientific books and papers, he comprehensively presented contemporary scientific problems and achievements for a wide range of readers and, which is particularly important, infected many generations of the readers of the journal Kvant (Quantum) with his love of science and cognition of the world. Moisei Isaakovich Kaganov (MIK) was born on June 4, 1921 in Kharkov. In 1939, he was admitted as a student to the Department of Physics at the Kharkov State University, but his studies did not last long. In December of the same year, MIK was conscripted into the army. He was in the war from beginning to end, serving till early 1946. In 1946, MIK returned to the university and, having done two diploma studies with his fellow student Viktor Moiseevich Tsukernik, graduated in 1949. This work and friendship between students were the beginning of their years-long fruitful collaboration in a whole number of fields, mainly in the theory of magnetic phenomena. The subject of one study about absorption of electromagnetic radiation by a spin wave system was proposed by Aleksandr Ilyich Akhiezer, and another one concerning the permittivity of a polycrystal was proposed by Ilya Mikhailovich Lifshitz. MIK considered I M Lifshitz to be his teacher. The cooperation with I M Lifshitz lasted many years and with time transformed into a strong friendship. Simultaneously, MIKworked a long time together with A I Akhiezer. In October of 1949,MIK began working at the Ukrainian Institute of Physics and Technology (UIPT), where he remained till April 1970. In 1970, invited by P L Kapitza, he and I M Lifshitz left for Moscow for the Institute of Physical Problems (IPP, now Kapitza Institute), where he worked for 24 years until his retirement in 1994. Both in Kharkov and in Moscow, MIK combined his scientific work with teaching activity. He first taught at Kharkov State University and then became a professor at Lomonosov Moscow State University, where he delivered courses on the electron theory of metals and quantum solid-state theory, both very popular with students. After MIK retired in 1994, he went to Boston in the USA, where one of his daughters had settled. The range of MIK's scientific interests spanned from the problems of classical electrodynamics of continuum media to practical problems of the physics of metals. In the early 1950s, at the cryogenic laboratory of UIPT, experiments on solidstate physics were started, and MIK, together with I M Lifshitz, got involved in the electron theory of metals. This became a basic subject for MIK for many years. One of his first papers in this field that became widely known was ``Kinetics of superconductivity destruction'' (I M Lifshitz, M IKaganov,Dokl. Akad. Nauk SSSR, 1953, v. 90, p. 579), in which the authors calculated the electromagnetic field distribution in a layer of normal metal emerging on a sample surface when superconductivity gets destroyed. In a normal metal layer, either a normal or an anomalous skin effect is realized, depending on the field oscillation frequency and the electron free path. According to MIK, he got to take part in that study as an expert on the anomalous skin effect. MIK returned to the skin effect time and again. Together withMYa Azbel', he formulated the theory of an anomalous skin effect in metals with an arbitrary electron spectrum (Dokl. Akad. Nauk SSSR, 1955, v. 102, p. 49). Together with VMTsukernik, he solved the problem of the influence of thermoelectric forces on the skin effect in metals (Zh. Eksp. Teor. Fiz., 1958, v. 35, p. 474 [Sov. Phys. JETP, 1959, v. 8, Uspekhi Fizicheskikh Nauk 190 (2) 221 ± 222 (2020) Translated by M V Tsaplina PERSONALIA PACS number: 01.60.+q

Markovich Khalatnikov, the outstanding Soviet and Russian theoretical physicist. IMKhalatnikov's scientific activity is diverse and covers the majority of areas of modern theoretical physics Ð from the theory of superfluidity to quantum field theory and the theory of relativity. Isaak Markovich was an initiator of the foundation of the Landau Institute of Theoretical Physics of the USSR Academy of Sciences (now the Russian Academy of Sciences Ð RAS), which he headed from 1965 to 1992. Isaak Markovich Khalatnikov was born on October 17, 1919 in the town of Ekaterinoslav (after 1926 Dnepropetrovsk, now Dnepr, Ukraine). He studied at Dnepropetrovsk State University and graduated from there in 1941. When a university student, Isaak Markovich began to take the exams for the theoretical minimum with Lev Davidovich Landau, who invited Isaak Markovich to become his postgraduate student. However, this plan went unfulfilled because of the war, during which IsaakMarkovich was in the active army in the air defense forces. After demobilization, Isaak Markovich entered the postgraduate course of the Institute for Physical Problems of theUSSRAcademyofSciences,where, underLDLandau's guidance, he became engaged in the theory of superfluidity. He made an underlying contribution to this field, where he was the leading theoretician for many years. He derived equations describing the dynamics of elementary excitations in superfluid liquid helium, formulated the theory of relaxation processes, considered various hydrodynamic phenomena (including shock waves), studied the hydrodynamics and kinetics of superfluid solutions of helium isotopes, and constructed the theory of temperature jump at the interface between superfluid helium and a solid body (Kapitza jump). All of this work was carried out in close connection with experiment and, undoubtedly, exerted a strong stimulating influence on the development of studies of superfluidity all over the world. In 1953, Isaak Markovich defended his doctoral thesis, in which he summed up his research in the theory of superfluid helium. Rather notable were the names of panel members at this defense: NNBogoliubov, V LGinzburg, and I M Lifshitz. In 1946, I M Khalatnikov was invited to participate, as part of L D Landau's group, in the Soviet Atomic Project. He organized numerical calculations concerning first the nuclear and then the thermonuclear bomb. During this work, he developed original numerical methods, in particular, he constructed implicit numerical schemes and solved the problem of numerical scheme stability. All this allowed successful calculations for the project to be carried out. For these achievements, I M Khalatnikov was rewarded with the USSR State Prize. After the postgraduate course, I M Khalatnikov continued working at the Theoretical Department of the Institute for Physical Problems. In the second half of the 1950s, he implemented studies devoted to the theory of Fermi liquids: he analyzed kinetic phenomena in such a liquid and formulated the theoryof light scattering in it. IMKhalatnikov formulated canonical methods (Lagrangian and Hamiltonian) in the hydrodynamics of quantum liquids, convenient for examining nonlinear phenomena. The work of I M Khalatnikov (together with LD Landau) devoted to the theory of sound absorption near second-order phase transition points came to underlie the dynamic theory of phase transitions. Isaak Markovich summarized his studies of the physics of quantum liquids in the monograph, An Introduction to the Theory of Superfluidity, which was published in 1971 and has been a handbook for all physicists engaged in this subject. The work on mixtures of superfluid Fermi liquids and superfluid Bose liquids (together with G E Volovik and V P Mineev) proved to be useful in experimental studies of quantum gas mixtures obtained through laser cooling. Uspekhi Fizicheskikh Nauk 189 (10) 1121 ± 1122 (2019) DOI: https://doi.org/10.3367/UFNr.2019.08.038651 Translated by M V Tsaplina PERSONALIA PACS number: 01.60.+q

Исаак Маркович Халатников (к 90-летию со дня рождения), Абрикосов А.А., Андреев А.Ф., Гинзбург В.Л., Горьков Л.П., Дзялошинский И.Е., Захаров В.Е., Минеев В.П., Новиков С.П., Питаевский Л.П., Покровский В.Л., Старобинский А.А., Элиашберг Г.М.

Герасим Матвеевич Элиашберг (К шестидесятилетию со дня рождения), Андреев А.Ф., Бычков Ю.А., Горьков Л.П., Ивлев Б.И., Иорданский С.В., Копнин Н.Б., Левитов Л.С., Минеев В.П., Перель В.И., Питаевский Л.П., Покровский В.Л., Рашба Э.И., Халатников И.М.

The dynamics of isolated vortices in a planar magnet is considered at temperatures above the Kosterlitz–Thouless transition. The spectrum of collective modes is determined in the self-consistent field approximation. The force acting on vortices in an external magnetic field is calculated and the frequency dependence of the dissipated power is established.