theoretical physicist and corresponding member of the Russian Academy of Sciences (RAS), Igor Ekhiel'evich Dzyaloshinskii. A disciple and colleague of the legendary Lev Davidovich Landau, one of the founders of the Institute of Theoretical Physics (ITP) of RAS, editor of the journal Zhurnal Eksperimental'noi i Teoreticheskoi Fiziki (ZhETF Ð J. Exp. Teor. Phys.) and Pis'ma v ZhETF (JETP Lett.), professor at Moscow Institute of Physics and Technology (MIPT), the faculty of Mechanics and Mathematics of Lomonosov Moscow State University (mech.math. MSU), and theUniversity of California, Irvineì this is a short list of highlights in the scientiéc biography of Igor Ekhiel'evich. The scientific interests of Dzyaloshinskii cover the whole spectrum of condensed media theory; most of his papers have been widely recognized. Already in his younger days, Dzyaloshinskii became a leader in the community of the physics of magnetic phenomena and presented such results as the prediction of the `magnetoelectric effect,' the introduction of the `Dzyaloshinskii ±Moriya interaction,' and the theory of helical superstructures and commensurability effects. This topic is in the list of his publications for today: the epoch of multiferroics that came in the 2000s was, in fact, based on the predictions made more than half a century before by the young scientist I E Dzyaloshinskii. These studies were included in the candidate thesis Dzyaloshinskii defended in 1957. When speaking at the defense, Landau, who was not lavish in giving praise, said that Dzyaloshinskii was one of the most talented young theoreticians whom he had met in recent years. During that same time, the temperature diagram technique was developed. It was included in the written (together with A A Abrikosov and L P Gor'kov) handbook of several generationsÐMethods of Quantum Field Theory in Statistical PhysicsÐthat was awarded the 1989 L D Landau Prize. The book (``AGD'' or the ``Green Book'' as referred to by many generations of students, postgraduates, and research workers at ITP) laid foundation of the scientific language used to date by theoretical physicists around the world. The fundamental contributions due to Igor Ekhiel'evich involve the microscopic theory of van der Waals forces, onedimensional systems of interacting particles, quantum liquids and crystals, spin glasses, topological defects in magnets and liquid crystals (incidentally, it was precisely Dzyaloshinskii who introduced in Russian theoretical physics the idea that liquid crystals are an important area of application of general principles), exactly solvable models, an original renormalization group for high-temperature superconductors, states with time reversal symmetry violation. The scientific and pedagogical achievements of I E Dzyaloshinskii are well known and, in particular, were described in detail in previous well wishes marking milestones. It so happens that most of us (disciples and colleagues of I E Dzyaloshinskii) took part in these very celebrations in the journal Uspekhi Fizicheskikh Nauk (UFN) (see UFN 162 (1) 139 (1992); UFN 171 (2) 227 (2001); UFN 181 (2) 231 (2011)) (Physics±Uspekhi 35 (1) 49 (1992), Physics±Uspekhi 44 (2) 213 (2001), Physics±Uspekhi 54 (2) 221 (2011)). However, new interesting and important work by Dzyaloshinskii appeared recently. In particular, noteworthy are two of his studies that predicted theoretically (and then revealed experimentally using muon spectroscopy methods in an etalon Cr2O3 magnetoelectric) a very interesting and nontrivial phenomenon. Namely, it turns out that, in a certain geometry, electric charges induce a magnetic field with quadrupole and monopole symmetry on a magnetoelectric antiferromagnet surface, both in the sample itself and in the surrounding space. I E Dzyaloshinskii continues to work and, in this milestone year, is finishing preparation of a paper, in collaboration with an international group of experimentalists, on the inverse electrocaloric effect in ion liquids (predicted theoretically in an earlier study undertaken by Dzyaloshinskii and Obukhov). Uspekhi Fizicheskikh Nauk 191 (2) 223 ± 224 (2021) Translated by M V Tsaplina PERSONALIA PACS number: 01.60.+q

Academy of Sciences Yurii Moiseevich Kagan passed away on June 4, 2019. Quite recently, on July 6, 2018, Yurii Moiseevich celebrated his 90th birthday. In this connection, the journal Uspekhi Fizicheskikh Nauk published a Personalia column (Usp. Fiz. Nauk 188 799 [Phys. Usp. 61 714 (2018)]) in which colleagues and friends heartily congratulated Yurii Moiseevich on this anniversary and recounted the main stages of his life and his most important achievements. Yu M Kagan was born in Moscow in 1928. In the hard war years, young Yu M Kagan worked at a plant and attended an evening school for working youth. When he was 16, he entered the Moscow Aviation Institute. He has then transferred to the Engineering Physics Faculty of theMoscow Mechanical Institute and graduated from it in 1950 with honors. At the same time, he passed all the exams of the famous `Theorminimum' of L D Landau, who invited him to the postgraduate course. However, he was sent to work on the USSR Atomic Project at the Ural Electrochemical Plant. Here, Yu M Kagan developed the general theory of the separation of isotopic gas mixtures in porous media. He suggested the idea of replacing the medium by a heavy `wall' gas. In 1954, YuMKagan defended his Candidate of Sciences thesis. He delivered a classified special course at the Ural Polytechnical Institute (Sverdlovsk). In 1956, he was invited to Moscow, to the Institute of Atomic Energy (IAE). After that time, the scientific life of Yu M Kagan was connected with the Russian Research Center, `Kurchatov Institute'. In 1959, he defended his thesis for the degree of Doctor of Sciences in Physics and Mathematics. Here, YuMKagan formulated the kinetic theory of gases with rotational degrees of freedom.He constructed the theory of transport phenomena in external fields and explained the nature of kinetic coefficients variations in a magnetic field (the Sentfleben effect). The results were included in textbooks and initiated extensive studies. The terms `Kagan vector' and `Kagan polarization' appeared. The latter effect was observed 25 years later at the Leiden laboratory. In the 1960s, Yu M Kagan began his research in the field of solid state physics. He developed the microscopic theory of nontransition metals and showed the decisive role of an electron liquid for their properties. The theory explained the nature of interion forces and predicted the appearance of singularities in the phonon spectrum. The results were confirmed experimentally. For this series of works, YuMKagan, alongwith his pupil and co-author EGBrovman, was awarded theMVLomonosov Prize of the USSR Academy of Sciences (1975). Yu M Kagan's studies of metallic hydrogen are widely known. He proved the existence of a metastable phase and analyzed its crystalline structure and vibrational spectrum. He found the equation of state, estimated the pressure of the transition to the metallic phase, and showed that only anisotropic structures are quasi-stable and that with increasing pressure the tendency appeared to form a liquid phase. He estimated the temperature of the high-pressure superconducting transition. A special place belongs to the studies of coherent phenomena in resonant interaction between nuclear radiation and crystals. In a series of studies carried out by Yu M Kagan and A M Afanasyev, the notion of collective excitation (a nuclear exciton) was introduced. The `Kagan± Uspekhi Fizicheskikh Nauk 189 (9) 1011 ± 1012 (2019) DOI: https://doi.org/10.3367/UFNr.2019.07.038631 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

theoretical physicists of the Soviet postwar generation, Academician of the Russian Academy of Sciences, Yurii Moiseevich Kagan. Yu M Kagan was born in Moscow in 1928. His father, Moisey Aleksandrovich, was a lawyer. He graduated from St. Petersburg University before the revolution. His mother, Rahil Solomonovna, was a physician. Yu M Kagan's early youth passed during the hard war years. In 1943, he began working in a war plant and attended a young workers' evening school. In autumn 1944, as a 16-year old boy, he entered the Moscow Aviation Institute. In February 1946, he was transferred to the second course of the Engineering Physics Faculty of the Moscow Mechanical Institute, which was founded for training specialists for the Atomic Project. He graduated from there in 1950 with honors. At the same time, he forwarded all the exams of the famous Theorminimum to L D Landau, who invited him to his postgraduate course. However, on graduating from the institute, he was sent to work on the USSR Atomic Project at the Ural Electrochemical Plant near Sverdlovsk. The plant was targeted at industrial production of uranium isotopes separated by the gasdiffusion method. When Yu M Kagan was working at the Central Laboratory of the plant, he developed the general theory of the separation of isotopic gas mixtures in porous media for the whole range of pressures from the Knudsen regime to the hydrodynamic one. Decisive here was his original idea of replacing a porous medium by a heavy `wall' gas with certain scattering characteristics. The problem of separating the n-component mixture on porous media was, in fact, reduced to the general diffusion problem for an (n‡ 1)-component mixture in free space. (Notably, several years later a similar idea was published by American physicists, but this time the heavy gas was referred to as `dustlike'.) In 1954, YuMKagan defended his Candidate of Sciences thesis. The same year, he was invited to deliver lectures at the specialized faculty of the Ural Polytechnical Institute. For three years he would go once a week to Sverdlovsk to give a classified course of lectures. In 1956, Yu M Kagan was invited to Moscow to the Institute of Atomic Energy (now the Russian Research Center `Kurchatov Institute'). Since that time to the present day, his scientific activity has been connected with this Institute. In 1959, he defended his thesis for the degree of Doctor of Phys.-Math. Sciences. Continuing to be engaged in the physics of molecular gases, Yu M Kagan formulated the kinetic theory of gases with rotational degrees of freedom. The introduction of the rotational moment vector to the theory, along with the velocity vector, radically changed the entire structure of the classical kinetic theoryofgases.TogetherwithLAMaksimov, he formulated the general theory of transport phenomena in molecular gases in external fields, which suggested, in particular, an explanation for the Senftleben effect (a change in the kinetic coefficients of a neutral molecular gas in a magnetic field), known since the 1930s. The theory initiated a wide scope of research in this country and abroad. Its resultsÐwhich, in fact, became classicalÐwere included in monographs and textbooks. The vector composed of the velocity vector and the rotational moment pseudovector, which is playing an essential role in the theory, is referred to as the `Kagan vector'. It is of interest that the alignment of rotational moments of molecules in a gas flow, referred to as `Kagan polarization', was directly measured experimentally in the Leiden laboratory 25 years after its theoretical prediction. Uspekhi Fizicheskikh Nauk 188 (7) 799 ± 800 (2018) DOI: https://doi.org/10.3367/UFNr.2018.06.038365 Translated by M V Tsaplina PERSONALIA PACS number: 01.60.+q

Vladislav Borisovich Timofeev, a Full Member of the Russian Academy of Sciences (RAS). Vladislav Borisovich is an outstanding experimental physicist, well known for his scientific results in the field of semiconductors and solid state physics. He has published over 200 scientific papers, including 16 reviews and two monographs. V B Timofeev graduated from the Faculty of Physics of Kiev State University in 1959 and stayed at the Department of Optics as a senior laboratory assistant. In 1962, he was appointed a senior research worker. In the following year, he was invited to the Chair of Optics at the University of Chernovitsy, where he took the position of Assistant Professor. In 1959, Vladislav Borisovich began active studies on the optical properties of semiconductors, with a particular emphasis on the examination of exciton±phonon spectra of cuprous oxide and phenomena related to spatial dispersion in the exciton region. The results obtained were acknowledged by the scientific community and underlay the Candidate's degree thesis, ``Quasiline absorption spectra of inorganic crystals'', which he defended in 1964. Beginning in 1966, V B Timofeev carried out some investigations concerned with the methods of precision spectrum interferential measurements and with holography, where he proposed methods of reference-free holographing. In 1967, V B Timofeev was invited to work as a Senior Researcher at the newly founded Institute of Solid State Physics (ISSP) RAS in Chernogolovka, not far from Moscow, which in due course became one of the leading research centers in Russia. V B Timofeev's entire further scientific activity and career are inseparably linked with ISSP RAS. At ISSP RAS, V B Timofeev has intensely and successfully developed a new direction related to the study of collective interactions in a system of nonequilibrium carriers and high-density excitons in semiconductors. V B Timofeev carried out research into nonequilibrium high-density electron±hole systems in direct band semiconductors (cadmium sulfide) and in semiconductors with an indirect forbidden band (germanium, silicon), in which he discovered basically new phenomena, namely, the exciton condensation to an electron±hole liquid in a polar direct-band semiconductor, a giant jump in photoconductivity under exciton metallization (Mott transition) in germanium, and exciton molecules in strained germanium and silicon crystals. He realized experimentally a new quantum objectÐa spin-oriented exciton gasÐand examined its quantum statistical properties at high densities. V B Timofeev comprehensively analyzed gas±liquid phase diagrams under exciton dielectric gas condensation to a metallic electron±hole liquid and, thus, laid the basis of the thermodynamics of nonequilibrium electron±hole systems. He revealed the giant probabilities of radiative recombination of exciton±impurity complexes in direct band semiconductors, as well as the phenomenon of their decay induced by the emission of acoustic phonons. V B Timofeev became a recognized leader in this new area in semiconductor physics. Part of the results of these studies was included in hisDoctor's degree thesis, ``Recombination emission of high-density excitons and nonequilibrium carriers'', successfully defended in 1975. V B Timofeev has often acutely changed the directions of his studies and has always achieved success. For instance, he was the first in the field of optical spectroscopy of hightemperature superconductors who carried out the study of inelastic light scattering attendant to the overgap excitations in oxide superconductors and revealed a strong scattering anisotropy resulting from the anisotropy of the superconducting gap. In the late 1980s, the scientific interests of V B Timofeev moved towards low-dimensional electron± hole and exciton systems in semiconductor heterostructures. Here, he discovered the effects of fractional quantization of Uspekhi Fizicheskikh Nauk 186 (9) 1027 ± 1028 (2016) DOI: 10.3367/UFNr.2016.08.037885 Translated by M V Tsaplina PERSONALIA PACS number: 01.60.+q

Владимир Валентинович Лебедев (к 60-летию со дня рождения), Андреев А.Ф., Габитов И.Р., Захаров В.Е., Иорданский С.В., Кац Е.И., Колоколов И.В., Коршунов С.Е., Трунин М.Р., Фалькович Г.Е., Фейгельман М.В., Хмельницкий Д.Е., Элиашберг Г.М.

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.