Video library

A.M. Sergeev, T. Tajima “Preface to the special issue of the journal "Physics-Uspekhi" ("Uspekhi Fizicheskikh Nauk"), dedicated to the publication of the materials of the forum 'USPEKHI-2021' ” Phys. Usp. 65 1115–1117 (2022)

P. Drobinski, A. Tantet “Integration of climate variability and climate change in renewable energy planning” Phys. Usp. 65 1119–1128 (2022)

The trajectory outlined in the Paris Agreement to keep global warming below 2ˆC dictates not only the timing but also the speed at which the transformation of our energy system must take place to decarbonize energy production. Complying with the Paris Agreement requires reducing the carbon content of energy by about 75% and therefore making a rapid transition from fossil production to production based on low-carbon technologies. Among these technologies are those based on renewable energies. The variability of the climate itself induces a fluctuating or even an intermittent production of variable renewable energy (solar, wind, marine), challenging the balance of the electricity grid. In this context, to speak of energy transition is to face the problem of increasing the penetration of low-carbon energy production while limiting the variability so as to ensure the socio-technical feasibility and economic viability. The problem is not simple, and the delicate balance between urgency (drastically reducing emissions) and utopia (choosing a strategy for low carbon energies and analyzing opportunities and obstacles) needs to be clearly defined.

Z.R. Ismagilov, E.V. Matus, L. Li “Catalytic methods of converting carbon dioxide into useful products to reduce the impact of coal generation on global climate change” Phys. Usp. 65 1139–1154 (2022)

Coal generation is one of the main sources of carbon dioxide emissions and makes a significant contribution to global climate change. In general, to curb global warming and to transition to a carbon-neutral economy, it is urgent to develop and improve methods for capturing and utilizing carbon dioxide. The most promising processing methods are those of catalytic conversion of CO₂ into valuable chemical products. This article discusses methods of CO₂ utilization, including synthesis reactions of low-molecular compounds (HCOOH, CO, H₂CO, CH₃OH, CH₄) and reactions to obtain high-molecular organic substances (carbamates RR'NCOOR'', carbonates (RO)₂CO, carboxylates RCOOH). The results of research on the creation of a number of effective nanosized catalysts for these processes are presented.

N. Li “New paradigm for civil nuclear energy. Perspectives from the hierarchy of energy sources and fundamental safety” Phys. Usp. 65 1155–1187 (2022)

This paper is a review and treatise extended in scope and based on a presentation made at the Uspekhi Forum on Climate Change and Global Energy. Following a brief overview of the history, status, and outlook of civil nuclear energy to present the key problems and challenges, this energy source is placed in a primary energy hierarchy on Earth with all classes of energy systems based on fundamental forces to reveal its unique characteristics that set civil nuclear energy qualitatively apart. A new paradigm is outlined with a distinct set of safety categories, design principles, and production methods that differ from conventional nuclear power, which leads to a global energy„ system solution for much broader development and deployment at scale in time to help mitigate climate change. Based on concepts and methods from studies of emergent properties in complex adaptive systems, we use a scaling method to analyze nuclear reactor safety and economics, and explicitly relate reactor unit scale, safety limits, and production volume to cumulative cost and capacity. Simultaneous improvement in and optimization of nuclear safety and economics are leading to small modular reactors (SMRs) and micro reactors (MRs) as exemplar technologies of the new paradigm. We show that select SMR and MR designs with deterministic fundamental safety should be manufactured, which can achieve substantial cost reductions as production volumes increase, following Wright's law observed in the majority of proven technologies. The new paradigm offers distinct and testable predictions, some of which have been partially tested, and some of which have surrogate tests from successful technologies and industries, which are also endowed with substantial transferable capabilities and capacities for implementation. The scaling principles and results should be generally applicable to other energy systems and the majority of manufactured goods.

S.N. Kalmykov “Solving scientific problems of nuclear power engineering as a source of 'green' energy” Phys. Usp. 65 1188–1192 (2022)

A way to prevent adverse global climatic change is to essentially alter the strategy of power generation, which is one of the major sources of greenhouse gases. A task of paramount economic importance is to ensure a balance among various energy sources, depending on the social economical features of a particular region. Major industrial regions cannot develop without highly concentrated energy sources, among which nuclear„ energy is actually the only 'green' one. However, progress in the nuclear power generation industry and an increase in its share in the total power generation both in Russia and worldwide depend on solving challenging scientific and technological problems related to safe processing of spent nuclear fuel and radioactive wastes. An urgent task is to develop a next-generation nuclear power industry based on a combination of thermal- and fast-neutron reactors, recycling of fissile nuclides, deep fractioning of radioactive wastes with subsequent 'afterburning' of long-lived radionuclides, and minimizing deep disposal in geological formations.

T. Tajima, A. Necas et al “East meets West again in order to tackle the global energy crises” Phys. Usp. 65 1193–1203 (2022)

The contemporary challenges of the impacts of human activities such as climate change induced by the increase in CO₂ emissions since the Industrial Revolution have been discussed throughout this Forum 'Uspekhi-2021', as have possible approaches to address these issues. Some have discussed nuclear approaches to remedy this situation, both fission-based and fusion-based. One of the challenges of the fission nuclear path is its radioactive spent nuclear waste, which can accumulate for a period longer than civilization has existed. If we recall, the first rapprochement between the East and West in 1955 was due to the desire to avoid nuclear confrontation between the East and West. East and West meet again, this time to find collaborative solutions to the global crises of climate change and other global environmental issues tightly related to worldwide energy issues. The meeting in 1955 launched the peaceful use of nuclear fusion energy, and since then we have witnessed, for example at this Forum 'Uspekhi-2021', the culmination of research in this area, like Norman Rostoker's aneutronic fusion approach driven by beam injection. At the previous meeting, Veksler also introduced collective acceleration using plasma to compactify accelerators. We are glad that we can show some of its fruits in the laser wakefield accelerator driving neutrons compactly and efficiently for the purpose of incinerating radioactive nuclear waste of transuraniums. These energy research efforts have also produced a path to follow in order to become carbon neutral or even carbon negative.

“Forum "Uspekhi-2021"” Phys. Usp. 64 1–2 (2021)

A.F. Andreev, L.A. Melnikovsky “Equilibrium shape of ⁴He crystals near critical surface directions” Phys. Usp. 61 1090–1093 (2018)

Conditions for applicability of mean field theory to the thermodynamics of the ⁴He crystal surface are determined. Although the faceting transition itself is of Berezinsky—Kosterlitz—Thouless type, the thermodynamic potential outside a narrow neighborhood of the transition temperature can be expanded in the spirit of the Landau theory of second-order phase transitions. The Ginzburg—Levanyuk parameter is estimated. The singular behavior of the surface stiffness near critical directions observed for essentially non-critical temperatures is explained.

Yu.E. Lozovik “New effects in and the control of the exciton system in quasi-two-dimensional structures” Phys. Usp. 61 1094–1099 (2018)

New effects in a system of quantum dipoles are discussed, such as anisotropic superfluidity in external fields, strong correlations, crystallization and the supersolid phase. Roton instability effects typical of strongly correlated Bose systems but also manifesting themselves in a weakly interacting system of titled dipoles are analyzed. Among the interesting physical realizations of the systems under consideration are dipole excitons in single or coupled quantum wells under a strong transverse electric field and in van der Waals heterostructures of new 2D materials such as transition metal dichalcogenides (TMDC). The use at ultralow temperatures of polar molecules or atoms with permanent or external-field-induced dipoles are also interesting realizations, as are Rydberg atoms in an external electric field.

A.A. Gorbatsevich, N.M. Shubin “Quantum logic gates” Phys. Usp. 61 1100–1115 (2018)

This paper reviews how solid-state or molecular structures in which information transformation processes are governed by quantum mechanical principles can be used to construct logic gates which, similar to classical complementary metal-oxide semiconductor (CMOS), structures do not consume power when in a stationary state. In the first generation quantum analogs of CMOS gates, logical state switching occurs by fast quantum-mechanical tunneling processes, but the transfer characteristics are determined by classical diffusion-drift carrier transport. The second generation quantum analogs of CMOS schemes are open quantum systems in which charge carrier transport occurs coherently. The development of atomic precision lithography technology will allow wide use of quantum molecular logic gates in traditional computer architectures.

O.A. Pankratov “Understanding surface states of topological insulators” Phys. Usp. 61 1116–1126 (2018)

Topological electron states were theoretically predicted by B.A. Volkov and O.A. Pankratov in 1985 as interface states in an inverted contact between IV—VI semiconductors with their bands mutually inverted. As became clear later, the `inverted' SnTe semiconductor is a topological insulator, and the inverted contact is an example of a topologically nontrivial interface. This paper discusses the key results of Volkov and Pankratov's 1985 work and examines the usefulness of the inverted contact model for explaining the close link between the topologically nontrivial bulk band structure and the topological surface states. An advantage of the model for getting a deeper insight into this link is that it allows for an analytical solution. An inhomogeneous semiconductor structure is described by an effective Dirac Hamiltonian, which was obtained analytically from a tight binding model for the band structure of IV—VI materials. This allows one to trace the relation between topological surface states and bands in the bulk. As a result, the spin texture of a topological state can be expressed explicitly in terms of the bulk characteristics. It turns out that the spin texture can be controlled by varying the surface band bending. Given the nontrivial spin polarization at the surface, it is interesting to take a look at the Ruderman—Kittel—Kasuya—Yosida. (RKKY) interaction between magnetic adatoms, which can serve for probing the spin distribution locally. This interaction shows a much more complex structure than the common RKKY coupling in a non-polarized Fermi gas. The analytical theory provides an explicit relation between the RKKY interaction at the surface of a topological insulator and the parameters of the bulk spectrum.

A.K. Zvezdin, M.D. Davydova, K.A. Zvezdin “Ultrafast spin dynamics and inverse spin Hall effect in nanostructures with giant spin-orbit coupling” Phys. Usp. 61 1127–1136 (2018)

The features of ultrafast spin dynamics excitation using high-intensity femtosecond laser pulses in magnetic materials are reviewed. Key mechanisms of a pump pulse action on the spin system of a magnetic material are discussed, including the inverse Faraday effect in yttrium-iron garnet; induced magnetic anisotropy in thulium orthoferrite; and thermal driving the magnetic system out of equilibrium in the case of the metallic ferrimagnet GdFeCo, which is a promising material for magnetic memory and terahertz spintronics. It was shown that, apart from using conventional magneto-optical methods for probing the magnetization dynamics in magnetic heterostructures, one can also use the inverse spin Hall effect, an approach that potentially enables the development of memory elements in which the ultrafast optical control of magnetization is combined with electric detection.

S.A. Tarasenko “Electron properties of topological insulators. The structure of edge states and photogalvanic effects” Phys. Usp. 61 1026–1030 (2018)

Integrating the ideas of topology and topological transitions into solid state physics has led to the theoretical prediction and subsequent experimental discovery of topological insulators, a new class of three- or quasi-two-dimensional dielectric crystalline systems exhibiting stable conducting surface states. This paper briefly reviews the electronic properties of topological insulators. The structure of edge and bulk electronic states in two- and three-dimensional HgTe-based topological insulators is described in particular detail. Recent theoretical and experimental results on the interaction of an electromagnetic field with topological insulators and on edge and surface photogalvanic effects are presented.

M.I. Panasyuk “Greisen—Zatsepin—Kuzmin effect: top—down and bottom—up view” Phys. Usp. 61 903–911 (2018)

In 1966, K. Greisen, and independently G.T. Zatsepin and V.A. Kuzmin, published evidence for the existence of a relic (GZK) cutoff in the proton energy spectrum of >5× 10¹⁹ eV ultra-high energy cosmic rays (UHECRs). Half a century of experimental ground-based UHECR research has resulted in a large amount of data on energy spectra, anisotropy and mass composition. The first space experiment to measure UHECRs was launched in 2016. This paper discusses the results of and prospects for experimental UHECR research in the light of the proposed theoretical model of GZK cutoff.

O.G. Ryazhskaya “Creation of the FIAN Neutrino Laboratory and underground laboratories” Phys. Usp. 61 912–920 (2018)

This paper describes the history of how the FIAN Neutrino Laboratory was created and how the key methods, later to underlie the construction of BUST (Baksan Underground Scintillation Telescope), ASD (Artemovsk Scintillation Detector), LSD (Liquid Scintillation Detector) and LVD (Large Volume Detector) underground facilities, were developed and first implemented. This work, initiated by G.T.’Zatsepin, was crucial for the development of underground physics and gave the Institute of Nuclear Research, RAS, a leadership role in experiments to study stellar collapse neutrinos. The paper discusses underground physics as an effective method of studying a wide class of rare processes related to cosmic rays, neutrino physics, neutrino astrophysics, and elementary particles. The latest LVD and LSD results on the search for stellar collapse neutrinos are discussed, and research on cosmic ray muon characteristics and on muon interaction products at various depths underground is reviewed.

A.S. Lidvansky “G.T. Zatsepin and birth of gamma-ray astronomy” Phys. Usp. 61 921–925 (2018)

The centenary of G.T. Zatsepin, a well-recognized authority in cosmic ray physics and nuclear and neutrino astrophysics, offers an opportunity both to retrospect the work he is well-known for and to take a look at some of his lesser known ideas, even to specialists. One example is his pioneering proposal to employ the Cherenkov emission from electromagnetic cascades in the upper atmosphere as a tool to search for local gamma-ray sources on the celestial sphere. First published by G.T. Zatsepin and A.E. Chudakov in 1961, the idea was immediately put into practice by the latter in constructing the world's first gamma-ray telescope in Crimea. Zatsepin and Chudakov's method is still today the basis for very high energy gamma-ray astronomy, with the number of discovered sources approaching two hundred. New grandiose projects that are currently underway in this rapidly developing field of astronomy hold promise for an order of magnitude increase in the sensitivity of the method.

A.Yu. Grosberg “Il'ya Mikhailovich Lifshitz. The 100th anniversary of the birth” Phys. Usp. 61 84–88 (2018)

In this paper, we attempt to review the historical context, development and present status of the ideas formulated by Ilya M. Lifshitz in the many fields of theoretical physics where he worked.

G.E. Volovik “Exotic Lifshitz transitions in topological materials” Phys. Usp. 61 89–98 (2018)

Topological Lifshitz transitions involve many types of topological structures in momentum and frequency-momentum spaces, such as Fermi surfaces, Dirac lines, Dirac and Weyl points, etc., each of which has its own stability-supporting topological invariant (N₁, N₂, N₃, Ñ₃, etc.). The Fermi surface and Dirac line topologies and the interconnection of objects of different dimensionality produce a variety of Lifshitz transition classes. Lifshitz transitions have important implications for many areas of physics. To give examples, transition-related singularities can increase the superconducting transition temperature; Lifshitz transitions are the possible origin of the small masses of elementary particles in our Universe; a black hole horizon serves as the surface of Lifshitz transition between the vacua with type-I and type-II Weyl points, etc.

S.K. Nechaev, K. Polovnikov “Rare-event statistics and modular invariance” Phys. Usp. 61 99–104 (2018)

Simple geometric arguments based on constructing the Euclid orchard are presented that explain the equivalence of various types of distributions that result from rare-event statistics. In particular, the spectral density of the exponentially weighted ensemble of linear polymer chains is examined for its number-theoretic properties. It can be shown that the eigenvalue statistics of the corresponding adjacency matrices in the sparse regime show a peculiar hierarchical structure and are described by the popcorn (Thomae) function discontinuous in the dense set of rational numbers. Moreover, the spectral edge density distribution exhibits Lifshitz tails, reminiscent of 1D Anderson localization. Finally, a continuous approximation for the popcorn function is suggested based on the Dedekind-function, and the hierarchical ultrametric structure of the popcorn-like distributions is demonstrated to be related to hidden SL(2, Z) modular symmetry.

E.I. Kats “Nontraditional phase transitions in liquid crystals” Phys. Usp. 60 949–953 (2017)

According to classical textbooks on thermodynamics or statistical physics, there are only two types of phase transitions—continuous, or second-order phase transitions in which the latent heat L is zero, and the first-order phase transitions in which L ≠ 0. Present day textbooks and monographs also mention yet another, stand-alone type—the Berezinskii—Kosterlitz—Thouless transition, which is relevant only in two dimensions and which shares some features with the former two. This paper discusses examples of nontraditional thermodynamic behavior (i.e., which is inconsistent with the theoretical phase transition paradigm now universally accepted). For phase transitions in smectic liquid crystals, mechanisms for nonconventional behavior are proposed and predictions they imply are examined.

V.V. Brazhkin “Phase transformations in liquids and the liquid—gas transition in fluids at supercritical pressures” Phys. Usp. 60 954–957 (2017)

It is an experimental fact that in the neighborhood of melting curves, including those measured at above-critical pressures and temperatures, all fluids have some short- and intermediate-range order and their excitation spectra contain high-frequency shear waves. At high pressure both smooth and sharp first-order phase transformations involving changes in liquid structure and properties can occur between various liquid states. However, at sufficiently high temperatures any liquid loses its identity and turns into an unstructured dense gas in which only longitudinal waves can propagate. This paper discusses theoretical and experimental evidence for the existence of a boundary between a 'solid-like' melt and a dense gas at supercritical pressures.

D.H. Reitze “The first detections of gravitational waves emitted from binary black hole mergers” Phys. Usp. 60 823–829 (2017)

The LIGO Scientific Collaboration and the Virgo Collaboration carried out the inaugural 'O1' observing run from September 12, 2015 through January 19, 2016 using the newly commissioned Advanced LIGO interferometers located in Hanford, WA and Livingston, LA. During the O1 run and the O2 run currently underway, three definitive detections of gravitational waves occurred, each produced during the mergers of binary stellar mass black hole system. A fourth candidate gravitational-wave event was identified, also likely produced from a binary black hole merger. The detected gravitational waveforms allow for the inference of the intrinsic astrophysical parameters of the merging binary systems as well as the resulting black hole produced by the mergers. The first detect detections of gravitational waves confirm the existence of binary black hole systems, and have profound implications for astrophysics using gravitational waves as a new and powerful probe of the universe.

V.N. Rudenko “Gravitational-wave experiment in Russia” Phys. Usp. 60 830–842 (2017)

A brief summary is given of the experimental research into the detection of extraterrestrial gravitational radiation performed in Russia since the late 1960s. Various aspects of this topic are reviewed, including experiments with resonant detectors, geophysical methods for detecting low-frequency gravitational waves, and high frequency versions of the gravitational `Hertz experiment'. A description is given of the current situation concerning the unique optoacoustic gravitational detector OGRAN mounted in the underground laboratory of the Baksan neutrino observatory, Institute for Nuclear Research, Russian Academy of Sciences. Prospects are examined for building a Russian Federation based long base gravitational wave interferometer integrated into the global network of gravitational antennas.

G.S. Bisnovatyi-Kogan, S.G. Moiseenko “Gravitational waves and core-collapse supernovae” Phys. Usp. 60 843–850 (2017)

A mechanism of formation of gravitational waves in the Universe is considered for the nonspherical collapse of matter. Nonspherical collapse results are presented for a uniform spheroid of dust, and a finite entropy spheroid. Numerical simulation results on core-collapse supernova explosion are presented for the neutrino and magneto-rotational models. These results are used to estimate the nondimensional amplitude of the gravitational wave with frequency ν ~ 1300 Hz, radiated during the collapse (calculated by the authors in 2D) of the rotating nucleus of a pre-supernova with a mass of 1.2 M_⊙. This estimate agrees well with many other calculations (presented in this paper) which have been done in 2D and 3D settings and which rely on more exact and sophisticated calculations of the gravitational wave amplitude. The formation of the large scale structure of the Universe in the Zel'dovich pancake model involves the radiation of very long-wavelength gravitational waves. The average amplitude of these waves is calculated from the simulation, in the uniform spheroid approximation, of the nonspherical collapse of noncollisional dust matter, which imitates dark matter. It is noted that the gravitational wave radiated during a core-collapse supernova explosion in our Galaxy is of sufficient amplitude to be detected by existing gravitational wave telescopes.

I.M. Dremin “Unexpected interaction properties between high energy protons” Phys. Usp. 60 333–344 (2017)

Experimental data on proton-proton interactions in high energy collisions show that the elastic-to-inelastic scattering ratio varies in an unexpected way with collision energy, the decrease at comparatively low energies being followed by a factor of over 1.5 (!) increase in the energy range from 11—60 GeV at the Intersecting Storage Rings (ISR) to 7—13 TeV at the Large Hadron Collider (LHC). Intuitive expectations would be that, classically, proton break-up processes will continue increasing in number compared to proton survivals. It can be assumed that this surprising effect is either due to the asymptotic freedom property or to the collision time being extremely short at such high energies. The unquestionable unitarity principle is combined with the available elastic scattering data to gain new insight into the spatial shape of the interaction region of colliding protons. How this region evolves at energies currently used is considered and some predictions on its behavior at still higher energies are made for different assumptions concerning the relative roles of elastic scattering and inelastic processes. The shape can transform rather drastically if elastic processes keep rising in proportion. There is an unexpected corollary to this unexpected property. The possible origins of the effect and its relation to strong interaction dynamics are discussed.

V.V. Kocharovsky, V.V. Zheleznyakov et al “Superradiance: the principles of generation and implementation in lasers” Phys. Usp. 60 345–384 (2017)

The electrodynamics of active continuous media is used to theoretically examine collective spontaneous emission regimes of dipole oscillator ensembles. Recent experiments that observed the superfluorescence phenomenon are reviewed. The focus is on propagation and interaction effects experienced by the inhomogeneous waves of active centers' polarization and electromagnetic field. The superradiant laser dynamics are examined and prospects for realization of superradiant lasers using low-Q cavities are discussed.

V.I. Ritus “V.L. Ginzburg and the Atomic Project” Phys. Usp. 60 413–418 (2017)

This paper is an expanded version of the author's talk presented at a session of the Division of Physical Sciences of the Russian Academy of Sciences celebrating the 100th anniversary of V.L.  Ginzburg's birth. Tamm's special group was organized in June 1948 with the task to clarify the feasibility of constructing a hydrogen bomb. Having checked and confirmed the calculations by Ya.B.  Zel'dovich's group, the Tamm group proposed an original hydrogen bomb design, which, following A.D.  Sakharov's idea, consisted of an atomic bomb surrounded spherically by uranium and heavy water layers: heavy water, on V.L. Ginzburg's suggestion, was replaced by higher-calorie solid lithium-6 deuteride. The ionization compression of deuterium by uranium, both heated by the atomic bomb explosion, greatly accelerates nuclear reactions in deuterium and uranium and increases the total energy release. Upon their approval by the top KB-11 researchers, the Atomic Project leadership, and the Government, the proposals were implemented in the RDS-6s bomb, which was successfully tested 12 August 1953. Lithium-6 deuteride turned out to be a convenient multi-purpose nuclear fuel. The paper highlights the recognition by the leaders of the country and of the Atomic Project that fundamental science plays a crucial role in promoting scientists' ideas and proposals.

T.E. Kuzmicheva, A.V. Muratov et al “On the structure of the superconducting order parameter in high-temperature Fe-based superconductors” Phys. Usp. 60 419–429 (2017)

This paper discusses the synthesis, characterization, and comprehensive study of Ba-122 single crystals with various substitutions and various T_c's. The paper uses five complementary techniques to obtain a self-consistent set of data on the superconducting properties of Ba-122. A major conclusion of the authors work is the coexistence of two superconducting condensates differing in the electron-boson coupling strength. The two gaps that develop in distinct Fermi surface sheets are nodeless in the k_xk_y-plane and exhibit s-wave symmetry, the two-band model represents a sufficient data description tool. A moderate interband coupling and a considerable Coulomb repulsion in the description of the two-gap superconducting state of barium pnictides favor the s⁺⁺-model.

I.V. Antonova “2D printing technologies using graphene based materials” Phys. Usp. 60 204–218 (2017)

This paper reviews major research into the use of graphene and other multilayer materials in 2D printing technologies for fabricating modern electronics and photonics devices. The paper discusses methods for obtaining suspensions and properties of printed layers, provides examples and parameters of specific printed devices and outlines major trends in the field. Special emphasis is placed on the conceptual change in graphene suspension fabrication from using organic liquids to using water-based solution for stratifying graphite and fabricating liquid ink. The paper also considers the trend towards the use of increasingly graphene-rich ink, an approach whereby highly conductive printed layers can be obtained. The expansion of the range of used materials is also discussed.

V.V. Mayer, E.I. Varaksina, V.A. Saranin “A drop jumps to weightlessness: a lecture demo” Phys. Usp. 60 108–113 (2017)

The paper discusses the lecture demonstration of the phenomenon in which a drop lying on a solid unwettable substrate performs a jump when making the transition to weightlessness. An elementary theory of the phenomenon is given. A jump speed estimate is obtained for small and large drops. The natural vibrational frequency of a flying drop is determined. A full-scale model of Einstein's lift is described. Experimental and theoretical results are found to agree satisfactorily.

M.V. Sadovskii “High-temperature superconductivity in monolayers FeSe” Phys. Usp. 59 947–967 (2016)

V.B. Braginsky, I.A. Bilenko et al “Background to the discovery of gravitational waves” Phys. Usp. 59 879–885 (2016)

On 14 September, 2015, the two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) in the US recorded the first direct detection of gravitational waves. This paper reviews the contributions to this discovery by V.B. Braginsky's group at the Physics Department of Lomonosov Moscow State University.

A.M. Cherepashchuk “Discovery of gravitational waves: a new chapter in black hole studies” Phys. Usp. 59 910–917 (2016)

With the discovery of gravitational waves, a new space information channel has become available to scientists, and a new field of science, nonlinear dynamics of curved space-time (geometrodynamics for short) has been provided with an observational basis. The observation of gravitational waves is particularly interesting for understanding the nature of black holes. The observation of the last ring down stage during a binary black hole merger can in principle provide evidence for the existence of an event horizon for the newly formed black hole. The discovery of gravitational waves opens new possibilities for the massive discovery and investigation of new black holes in highly evolved binaries.

V.M. Lipunov “Astrophysical sense of the discovery of gravitational waves” Phys. Usp. 59 918–928 (2016)

The discovery of gravitational waves by the international collaboration LIGO (Laser Interferometer Gravitational-Wave Observatory)/Virgo on the one hand is a triumphant confirmation of the general theory of relativity, and on the other it confirms the general fundamental ideas on the nuclear evolution of the Universe baryon matter in binary stars. LIGO/Virgo may turn out to be the first experiment in the history of physics to detect two physical entities, gravitational waves and black holes.

V.L. Aksenov, A.M. Balagurov “Neutron diffraction on pulsed sources” Phys. Usp. 59 279–303 (2016)

The possibilities currently offered and major scientific problems solved by time-of-flight neutron diffraction are reviewed. The reasons for the rapid development of the method over the last two decades has been mainly the emergence of third generation pulsed sources with a MW time-averaged power and advances in neutron-optical devices and detector systems. The paper discusses some historical aspects of time-of-flight neutron diffraction and examines the contribution to this method by F.L. Shapiro whose 100th birth anniversary was celebrated in 2015. The state of the art with respect to neutron sources for studies on output beams is reviewed in a special section.

A.P. Pyatakov, A.S. Sergeev et al “Micromagnetism and topologic defects in magnetoelectric media” Phys. Usp. 58 981–992 (2015)

This paper briefly reviews research into magnetoelectric materials and multiferroics as domain-structured media. The review is focused on magnetoelectric phenomena in epitaxial iron garnet films (electrically induced displacement and tilting of domain boundaries) as a striking example of magnetoelectricity in micromagnetism. The paper also considers the effect of an electric field on other topological defects in magnetically ordered media, including Bloch lines and Bloch points at domain boundaries, magnetic vortices, and skyrmions.

A.V. Shchelokova, I.V. Melchakova et al “Experimental realization of invisibility cloaking” Phys. Usp. 58 167–190 (2015)

Advances in the studies of metamaterials pushed the development of invisibility cloaks which suppress the scattering by objects within certain frequency ranges. During recent years, there was a transition from a purely theoretical consideration of invisibility cloaks to its practical implementation. This paper is an overview of the current state of the art in the area of invisibility cloaks with an emphasis on experimental realization of such devices.

V.V. Mayer, E.I. Varaksina, V.A. Saranin “Simple lecture demonstrations of instability and self-organization” Phys. Usp. 57 1130–1135 (2014)

A dielectric liquid layer which has an electric field created inside it is proposed as a means for demonstrating the phenomenon of self-organization. The field is produced by distributed charge transferred by a corona discharge from the tip to the liquid surface. The theory of the phenomenon is presented. An analogy with the Rayleigh—Taylor instability is drawn and a comparison with the Benard instability is given. The practicality of the method for scientific and humanitarian audiences is examined.

G.R. Ivanitskii, A.A. Deev, E.P. Khizhnyak “Long-term dynamic structural memory in water: can it exist?” Phys. Usp. 57 37–65 (2014)

There is no experimental evidence to support the hypothesis that water retains a memory of mechanical, magnetic and electromagnetic influences it has been exposed to and of substances it has dissolved. After its solutes have been fully removed by repeated dilutions, the water does not remember of having contained them or of the external physical influences exerted upon it. There is no arguable reason that water should have a molecular information matrix capable of serving as a long-term memory.

I.S. Aranson “Active colloids” Phys. Usp. 56 79–92 (2013)

A colloidal suspension is a heterogeneous fluid containing solid microscopic particles. Colloids play an important role in our everyday life, from food and pharmaceutical industries to medicine and nanotechnology. It is useful to distinguish two major classes of colloidal suspensions: equilibrium and active, i.e., maintained out of thermodynamic equilibrium by external electric or magnetic fields, light, chemical reactions, or hydrodynamic shear flow. While the properties of equilibrium colloidal suspensions are fairly well understood, active colloids pose a formidable challenge, and the research is in its early exploratory stage. One of the most remarkable properties of active colloids is the possibility of dynamic self-assembly, a natural tendency of simple building blocks to organize into complex functional architectures. Examples range from tunable, self-healing colloidal crystals and membranes to self-assembled microswimmers and robots. Active colloidal suspensions may exhibit material properties not present in their equilibrium counterparts, e.g., reduced viscosity and enhanced self-diffusivity, etc. This study surveys the most recent developments in the physics of active colloids, both in synthetic and living systems, with the aim of elucidation of the fundamental physical mechanisms governing self-assembly and collective behavior.

V.V. Brazhkin, A.G. Lyapin et al “Where is the supercritical fluid on the phase diagram?” Phys. Usp. 55 1061–1079 (2012)

We discuss the fluid state of matter at high temperature and pressure. We review the existing ways in which the boundary between a liquid and a quasigas fluid above the critical point are discussed. We show that the proposed 'thermodynamic' continuation of the boiling line, the 'Widom line', exists as a line near the critical point only, but becomes a bunch of short lines at a higher temperature. We subsequently propose a new 'dynamic' line separating a liquid and a gas-like fluid. The dynamic line is related to different types of particle trajectories and different diffusion mechanisms in liquids and dense gases. The location of the line on the phase diagram is determined by the equality of the liquid relaxation time and the minimal period of transverse acoustic excitations. Crossing the line results in the disappearance of transverse waves at all frequencies, the diffusion coefficient acquiring a value close to that at the critical point, the speed of sound becoming twice the particle thermal speed, and the specific heat reaching 2k_B. In the high-pressure limit, the temperature on the dynamic line depends on pressure in the same way as does the melting temperature. In contrast to the Widom line, the proposed dynamic line separates liquid and gas-like fluids above the critical point at arbitrarily high pressure and temperature. We propose calling the new dynamic line the 'Frenkel line'.

V.D. Shiltsev “High energy particle colliders: past 20 years, next 20 years and beyond” Phys. Usp. 55 965–976 (2012)

Particle colliders for high-energy physics have been in the forefront of scientific discoveries for more than half a century. The accelerator technology of the colliders has progressed immensely, while the beam energy, luminosity, facility size, and cost have grown by several orders of magnitude. The method of colliding beams has not fully exhausted its potential but has slowed down considerably in its progress. This paper briefly reviews the colliding beam method and the history of colliders, discusses the development of the method over the last two decades in detail, and examines near-term collider projects that are currently under development. The paper concludes with an attempt to look beyond the current horizon and to find what paradigm changes are necessary for breakthroughs in the field.