We present an analytic description of the generation of undulator radiation (UR) harmonics in a generalized elliptic undulator with field harmonics. The obtained analytic expressions for generalized Bessel and Airy functions describe the UR spectral lines and radiation intensity in the general and particular cases of two-frequency planar and helical undulators and also for other elliptic and planar

Based on generalizations of numerous measurements and calculations, the influence of the low-frequency part of the atmospheric turbulence spectrum, directly adjacent to the inertial interval, on the statistical characteristics of fluctuations of optical waves propagating in the atmosphere is analyzed. The measured atmospheric turbulence spectra are compared with isotropic models. The outer scale of

Binary systems (layers) and multicomponent layers with bilayer thicknesses varying from microns to a few nanometers are considered. A strong dependence of the microstructure formation on the deposition conditions (the magnitude of the bias potential, the flow of inert and reactive gases, the ion beam power (current density) supplied to the target) is found. General regularities in the change in the

We describe the recently discovered phenomenon of the formation of an extended luminous structure at the bend of the channel of a high-voltage pulse discharge. It is called the apokamp (from the Greek words απ — ‘from’ and κάμπη — ‘bend’), and the discharge as a whole is referred to as apokampic. In the course of experimental and theoretical studies, it is shown that the apokamp is a narrow streamer

The present work is devoted to describing the current state of the collective transport theory in liquids. In this connection, the results of MD-modeling of the root mean square displacement and the velocity autocorrelation function of a molecule (VACFM) at large enough times are discussed. The characteristic function allowing one to estimate the relative value of collective contributions to the self-diffusion

Three quarters of a century ago, in his paper “Quadrupole and dipole γ-emission from nuclei” [J. Phys. USSR 8 331 (1944); Zh. Eksp. Teor. Fiz. 15 81 (1945)], A B Migdal introduced the concept of quantum collective excitation modes into nuclear physics, thereby predicting the phenomenon of giant dipole resonance (GDR). GDR research has had an enormous influence on the formation of modern concepts relating

Evaporation and condensation processes are intensely used in various fields of technology. Efforts to understand the features of film boiling of various liquids, primarily superfluid helium, inevitably lead to studying the strongly nonequilibrium processes of heat transfer from the heating surface through the vapor to the condensed phase. Theoretical studies of evaporation and condensation of single-component

A modification of the of high-speed high-resolution X-ray absorption spectroscopy (Quick Extended X-ray Absorption Fine Structure, QEXAFS) method based on an adaptive bending element of X-ray optics is described. This technique was implemented at the Langmuir station of the Kurchatov Synchrotron Radiation Source (KISI-Kurchatov). The absorption spectrum of a model sample, bromine in a sodium bromide

We present an introduction to the theory of dispersive shock waves in the framework of the approach proposed by Gurevich and Pitaevskii (Zh. Eksp. Teor. Fiz., Vol. 65, p. 590 (1973) [Sov. Phys. JETP, Vol. 38, p. 291 (1974)]) based on Whitham’s theory of modulation of nonlinear waves. We explain how Whitham equations for a periodic solution can be derived for the Korteweg–de Vries equation and outline

The review is devoted to the current state of research in one of the topical areas of the physics and chemistry of two-dimensional materials — the study of atomically thin films. The structure and properties of atomically thin monoelemental films, such as 2D iron, gold, and lithium, as well as silicene, germanene, borophene, etc., are described in detail. Two-dimensional films of metallic compounds

It is shown that the lack of objective existence of the results of quantum measurements of the state of collapse of the state vector of a remote localized system cannot be proved by an experiment using the reality of violation of Bell’s inequality in the Clauser–Horne–Shimony–Holt form. Arguments of a general nature and a specific calculation example confirming this conclusion are also given.

Discussed are the genesis of the concept of the relativistic runaway electron avalanche (RREA) and its mechanism as an analog of the Townsend’s avalanche, but capable of developing, unlike the latter, in weak thundercloud electric fields. Thanks to this, it was possible to overcome difficulties while interpreting results of observations of penetrating emission enhancements in thunderstorm atmospheres

Potassium, rubidium, aluminum, iron, nickel, and tin embedded atom models (EAMs) have been used as examples to ascertain how well the properties of a metal are described by EAM potentials calculated from the shape of shock adiabats and/or static compression data (from a function of cold pressure). Verification of the EAM potential implies an evaluation of its predictive power and an analysis of the

Within the framework of the Landau–Ginzburg (LG) theory, the kinetics of polarization switching in ferroelectric crystals and the transition from domain switching to homogeneous switching in nanosized single-crystal films are considered. It is shown that homogeneous (nondomain) switching can be described in LG theory terms only for two-dimensional ferroelectrics. A review of the experimental results

The recovering procedure of the electron–phonon interaction (EPI) functions from the additional nonlinearities of the current-voltage curve (I−V curve) of point contacts associated with an excess current is considered. The approach proposed takes into account both inelastic scattering, which causes suppression of the excess current in the reabsorption of nonequilibrium phonons by electrons undergoing

Progress in research aimed at combating neurodegenerative diseases requires a systematic biophysical analysis. It has been shown that the efficiency of cleaning the brain of metabolic and informational ‘toxins’ depends on the thresholds of excitation of neural networks and waves of ‘pollution and purification’ propagating inside the brain. This process affects the increase in the characteristic time

We present the theory of propagation and scattering of strongly refracting microwaves in turbulent inhomogeneous plasmas. We calculate the scattered signal amplitude in the case of a linear scattering regime in the Born approximation and in the case of multiple small-angle scattering. We discuss the possibility of an analytic description of multiple Bragg backscattering in a closed form. Based on the

A review of many-body effects in exciton ensembles in semiconductors is given with the emphasis on two-dimensional systems: structures with single and double quantum wells and with quantum microcavities. The Bose–Einstein condensation effect, an accumulation of a macroscopic number of excitons in the ground state of the system, is discussed. The known prohibition on condensation in low-dimensional

Key experimental studies (mainly pulse heating) aimed at obtaining the physical properties of the most refractory substance — graphite — in the temperature range of 2000–8000 K are discussed. The properties considered are enthalpy, input (Joule) energy, thermal expansion, specific heat, and electrical resistance, as well as their dependence on the level of applied pressure. The results obtained by

Arrays of quantum dots (QDs), i.e., semiconducting nanoparticles with typical sizes of 3–10 nm, have become more than merely an object of scientific research; they are now used in electronic devices. They are appealing mainly due to their optical properties, which depend on the QD size. Here, we consider the electronic properties of such arrays. These properties typically inherit the properties of

The latest results on the study of collective plasma excitations in two-dimensional electron systems based on AlGaAs/GaAs, AlGaAs/AlAs, and MgZnO/ZnO nanostructures and graphene are considered. Special attention is paid to the interaction of two-dimensional plasma with light. The results of experimental work on the discovery of a new family of plasma oscillations are presented. Possible avenues for

State-of-the-art studies of dielectric magnonics and magnon spintronics are reviewed. Theoretical and experimental approaches to exploring physical processes in and calculations of the parameters of magnonic micro- and nanostructures are described. We discuss the basic concepts of magnon spintronics, the underlying physical phenomena, and the prospects for applying magnon spintronics for data processing

Problems concerning irrotational flows past obstacles may have physical applications in magneto- and electrostatics, as well as in the description of hydrodynamical flows of incompressible fluids. It is shown that for a magnetic field flow (or a flow of incompressible fluid in the hydrodynamical case) around an ideally conducting (impermeable) screen of width D with a narrow slot of width Δ a substantial

Exoplanets represent a broad new class of astronomical objects, which became accessible for observations and studies only just before the end of the last century. Owing to continually improving techniques of ground-based observations, and especially observations from space, for a little bit more than two decades thousands of planetary systems of other stars have been discovered, and this process is

Among the observed variety of the natural phenomena reflected in experimental results, there are just a few physical features offering a view of a given fragment of the mosaic of physical laws in its entirety. One such remarkable fundamental feature is R, the ratio of the inclusive cross section of electron–positron annihilation into hadrons to the cross section of muon pair production in the Born

Precision X-ray methods for absolute and relative determination of crystal lattice parameters (interplanar distances) are described and compared, including the X-ray divergent-beam (Kossel) technique, the Bond method, the Renninger method, the back reflection method, the interference method, and the method of standards. It is shown that for most of the considered methods, a relative accuracy of ∼ 10−5

Electron transfer during low-energy ion scattering (LEIS) is discussed in the article. In most cases, the final charge state of ions/atoms scattered from a metallic surface is formed due to resonant charge transfer (RCT). The key concepts, model representations, and basic laws of electronic exchange are systemized in the article. For practical usage, RCT is primarily important for surface diagnostics

Under conditions of total internal reflection of a TM- (TE-) type of plane volume electromagnetic wave from the surface of a semi-infinite transparent anisotropic dielectric medium, a special type of fast improper surface wave can be formed (an exceptional surface wave). For these types of waves, the instantaneous flow of energy through the interface is zero. In this case, the reflection of a quasi-plane

A.S. Trushechkin, 2 E.O. Kiktenko, 2, 3, 4 D.A. Kronberg, 3, 4 and A.K. Fedorov 4 Steklov Mathematical Institute, Russian Academy of Sciences, Moscow 119991, Russian Federation Department of Mathematics and NTI Center for Quantum Communications, National University of Science and Technology MISiS, Moscow 119049, Russia Russian Quantum Center, Skolkovo, Moscow 143025, Russia Moscow Institute of Physics

On 5 June 2019, the Physical Sciences Division of the Russian Academy of Sciences (RAS) held a scientific session, entitled "Earth embosomed by the Sun: heliophysics and space weather" in the Conference Hall of the Lebedev Physical Institute, RAS. The meeting proceedings include the following presentations: (1) Bogachev S A (Lebedev Physical Institute, Russian Academy of Sciences, Moscow; Samara National

Study of the physical phenomena and processes on the Sun and in the heliosphere, a natural plasma laboratory, is based on near-earth and space-based observations and building models which help to obtain a general view of how the Sun was made and how it works, while allowing one to address the practical problems of solar activity influencing space weather and its impact on various areas of human activity

Solar wind — a plasma stream flowing out of the solar corona — is interesting both as a carrier of solar activity and as an example of a collisionless plasma. We present the main results of Russian studies in recent years. The original MHD model allows interpreting the bifurcation of the heliospheric current sheet during maximum activity years as occurring due to the quadrupole component of the heliomagnetic

We discuss the nature of additional (redundant from the point of view of selection rules) optical phonons observed in most crystals with ion–covalent bonds between atoms, including in their solid solutions. These ‘redundant’ phonons are located in the frequency range of the longitudinal–transverse splitting of fundamental phonons, where the real part of the crystal permittivity is negative. They are

Experimental results and theoretical concepts of anomalous phase transformations in alloys under severe plastic deformation (SPD) are reviewed. The unconventional phase and structural state of alloys that emerges as a result of SPD determines the unique combination of physical and chemical properties that is of interest for various applications in technology. The driving forces and possible mechanisms

Due to the increase in the spatial and temporal resolution of observations of the solar atmosphere, which is mainly associated with progress in space research, we now understand that the Sun’s activity not only is associated with large centers, but also extends to significantly smaller scales. Each new advance in experimental technology over the past 60 years has led to the discovery of more and more

At present, ptychography seems to be the most natural and efficient method for approaching the diffraction-limited optical resolution. The general setup of a ptychoscope does not contain refracting or focusing elements and includes a coherent illumination source, a translation stage for displacement of a macroscopic object, and a detector for recording transmitted or reflected radiation from the object

We present a brief review of the contemporary understanding of and topical problems in solar flare physics that can be clarified by methods of X-ray and gamma-ray astronomy. The review focuses on several issues, including the conditions and mechanisms of electron acceleration in solar flares, the flare energy distribution between thermal and nonthermal components, the gamma-ray emission from solar

Theory of spin noise in low dimensional systems and bulk semiconductors is reviewed. Spin noise is usually detected by optical means, continuously measuring the rotation angle of the polarization plane of the probe beam passing through the sample. Spin noise spectra yield rich information about the spin properties of the system including, for example, $g$-factors of the charge carriers, spin relaxation

In 2018 the Belle II experiment, aimed at detailed studies of B-mesons, started operation at the electron-positron collider SuperKEKB at KEK (Japan). This was preceded by a long and quite successful work of the B-factories of previous generations, including the Belle experiment for which Belle II is a successor. This experiment is unique and has no analogues or competitors in the world. The spectrum

The concepts of the physics of metallic alloys regarding the driving forces of diffusion phase transformations, the nature of solid solutions, the chemical interatomic interaction energy, the principles of plotting phase diagrams, and the principles of heat treatment of alloys are critically reviewed. The ordering-separation phase transition, which is caused by the recently detected property of alloys

Concentrated vortices are spatially localized structures with nonzero vorticity surrounded by a potential flow. These structures include a broad class of mesoscale vortices, such as dust devils, water vortices, and fire vortices, as well as larger-scale and more intense tornados. From a rather broad class of concentrated mesoscale vortices, dust devils are selected as the simplest and most easily observable

The most interesting experimental results obtained in studies of 2D and 3D topological insulators (TIs) based on HgTe quantum wells and films are reviewed. In the case of 2D TIs, these include the observation of nonlocal ballistic and diffusion transport, the magnetic breakdown of 2D TIs, and an anomalous temperature dependence of edge-channel resistance. In 3D TIs, a record-setting high mobility (up

This article presents a brief history of the appearance of electron spin in relativistic wave equations. Dirac derived his wave equation in 1928 with the intention to obtain an equation for the 'simplest' particle with spin zero. But, as Dirac later announced at the European Conference on Particle Physics (Budapest, 4–9 July 1977), it was a big surprise for him that the equation described the states

The latest achievements in the area of terahertz spectrometers based on transient effects are presented. The potential to use these spectrometers in various applications demanding the composition analysis of multicomponent gas mixtures simultaneously with a high sensitivity (at the ppb level) and resolving power is considered. The results obtained with the use of transient terahertz spectroscopy for

Models of field (cold, autoelectron) emission from various types of carbon nanostructures, other than graphene, are described. The experimental results are compared with theoretical predictions.

Physical processes that determine the generation of ion beams with a high emission current density in electrohydrodynamic emitters are considered. Electrohydrodynamic effects, which are manifested in the features of ion emission, and the kinetics of ion interaction in high-density beams are discussed. The factors that determine the size of the emission zone, stability of emission at high and low currents

Large-distance ultraperipheral collisions of two relativistic ions are considered. The clouds of photons surrounding the ions are responsible for their distant electromagnetic interaction. The perturbative approach and the method of equivalent photons are described. It is shown that the total cross section of these collisions increases rapidly with increasing energy and is especially large for heavy

The ##IMG## [http://ej.iop.org/images/1063-7869/63/6/601/toc_tex_pu_8807_img1.gif] {$ k$} coefficient method proposed by Bondi is extended to the general case where the angle ##IMG## [http://ej.iop.org/images/1063-7869/63/6/601/tex_pu_8807_img2.gif] {$ \alpha$} between the velocity of a signal from a distant source at rest and the velocity of the observer does not coincide with 0 or ##IMG## [http://ej

A plasma with an anisotropic velocity distribution of particles in a magnetic field is considered. It is shown that the Weibel instability arises in the reference frame rotating together with the particles, for example, ions. When considered in the immobile reference frame, this instability is known as the Alfvén cyclotron instability.

A review of spectroscopic methods for observations of stars in searching for and studying exoplanets is presented. Instrumental errors in measuring radial velocities and strategies to decrease (or fundamentally eliminate) them are considered. The role of astrometric and photometric methods is pointed out. The results of the study of the chemical composition of parent stars and the spectroscopy of transit

Theoretical and observational evidence is examined to verify the hypothesis put forward by N S Kardashev that some of the double images of galactic nuclei can be entrances to the same wormhole.

Particle separation mechanisms and kinetics in granular materials in a gravity chute and under vibrational impact are analyzed. Special attention is given to separation and kinetics mechanisms operating under conditions of high heterogeneity of structural and kinematic characteristics of granular flows. An analysis of alternative expressions for the separation driving force arising from local and spatial

We present a critical review of recent attempts to introduce the new quantum ("Planckian") limit for the temperature dependence of inelastic scattering rate of electrons in metals. We briefly discuss the main experimental facts and some simple theoretical models explaining the linear in temperature growth of resistivity (starting from very low temperatures) in superconducting cuprates and some similar

Quantum entanglement is a powerful resource that revolutionizes information science, opens new horizons in communication technologies, and pushes the frontiers of sensing and imaging. Whether or not the methods of quantum entanglement can be extended to life-science imaging is far from clear. Live biological systems are eluding quantum-optical probes, proving, time and time again, too lossy, too noisy

It was previously shown that the experimental measurement of the lifetime of gas-phase negative ions formed in autoionization states during resonant electron capture by molecules is inherently fraught with inaccuracy due to adsorption of ions on the walls of the ionization chamber, with some of them surviving there and staying stabilized as 'eternal' till they eventually desorb back into the vacuum

This review is based on a talk by the authors at the field Scientific session of the Physical Sciences Division of the Russian Academy of Sciences devoted to the 60th anniversary of the Vereshchagin Institute for High Pressure Physics of the Russian Academy of Sciences. The dependence of phase-diagram characteristics and phase transitions on the shape of the intermolecular potential is reviewed and

The study of the interaction of electron beams with electromagnetic fields and of devices based on them is one of the central areas of the science of vibrations and waves. In the 20th century, Physics-Uspekhi published reviews devoted to the theory and description of new devices at that time. The theory and design of these devices and their place in the electromagnetic wave range have changed with

Dipole-dipole interaction between molecules of hydrogen-bonding polar liquids (HBPLs), which has a collective and long-range nature, determines the basic large-scale properties of such liquids. We present a two-scale phenomenological vector model of polar liquids (VMPLs), wherein the liquid is described by a polarization vector. The simplest version of this model satisfactorily reproduces the well-known

Review of the genuine black holes silhouettes. The isolated black hole is an invisible object in general relativity due to the infinite red-shift of photons moving from the black event horizon to a distant observer. Nevertheless, the dark shadow (silhouette) of the astrophysical black hole may be visible by a distant observer on the luminous background lensed in the black hole gravitational field.

The last 25 years has witnessed a wealth of publications on the creation of carbon materials whose compression bulk modulus and hardness are much higher than those of diamond. This review presents a critical analysis of these studies. Three groups of myths that have emerged lately are discussed. The first is related to the possibility of creating materials whose bulk moduli are significantly higher