arXiv subjects

A. V. Kats

Publications and source records attributed to A. V. Kats.

12 recordsLinked to original sources

arXiv2019

Electromagnetic Grazing Anomaly: Energy Flux Resonance Behaviour and Brewster Angle Analogy

The diffraction of electromagnetic waves at the surface periodic structures accompanied by strong anomalous effects in different diffraction orders is considered in great detail for high-contrast interfaces. We restrict our discussion to the TM polarization of the incident wave (the magnetic field is orthogonal to the plane of incidence) and the simplest geometry when the plane of incidence is orthogonal to the grating grooves. The most attention is focused on the strong maxima and minima of the energy flux density accompanying specific grazing propagation of some diffraction order. Relation to other anomalies, both Rayleigh and the resonance ones is discussed as well.

physics.optics↗

arXiv2013

The use of gravitational lenses in the study of distant galaxy mergers

Gravlenses are efficiently explored for detecting the most distant galaxies (up to z=10 redshifts). As an example of the role played by gravlenses we refer to the observation of the galaxy merger at z=3 (Borys, et al; Berciano Alba, et al). We derived solutions for the Smoluchowski kinetic equation for the mass function of galaxies, which describes mergers in differential approximation (minor mergers). It is shown that the evolution of the slope of luminosity function observed in the Ultra Deep Hubble Field (Bouwence et al) can be described as a result of explosive evolution driven by galaxy mergers.

astro-ph.CO↗

arXiv2013

Merger Driven Explosive Evolution of Distant Galaxies (Minor Mergers)

We derived solutions for the Smoluchowski kinetic equation for the mass function of galaxies, which describes mergers in differential approximation, where mergers with low-mass galaxies are the dominant factor. The evolution of the initial distribution is analyzed as well as the influence of the source represented by galaxies (halos) that separate from the global cosmological expansion. It is shown that the evolution of the slope of the power-law part of the luminosity function at a constant mass-to-luminosity ratio observed in the Ultra Deep Hubble Field can be described as a result of explosive evolution driven by galaxy mergers. In this case the exponent depends exclusively on the uniformity degree of merger probability as a function of mass.

astro-ph.CO↗

arXiv2013

Surface plasmon-polariton resonance at diffraction of THz radiation on semiconductor gratings

Resonance diffraction of THz HCN laser radiation on a semiconductor (InSb) grating is studied both experimentally and theoretically. The specular reflectivity suppression due to the resonance excitation of the THz surface plasmon-polariton is observed on a pure semiconductor grating and on semiconductor gratings covered with a thin striped layer of the residual photoresist. Presence of a thin dielectric layer on the grating surface leads to the shift and widening of the plasmon-polariton resonance. A simple analytical theory of the resonance diffraction on a shallow grating covered with a dielectric layer is presented. Its results are in a good accordance with the experimental data. Analytical expressions for the resonance shift and broadening can be useful for sensing data interpretation.

physics.optics↗

arXiv2008

Resonantly suppressed transmission and anomalously enhanced light absorption in ultrathin metal films

We study light diffraction in the periodically modulated ultrathin metal films both analytically and numerically. Without modulation these films are almost transparent. The periodicity results in the anomalous effects, such as suppression of the transmittance accompanied by a strong enhancement of the absorptivity and specular reflectivity, due to excitation of the surface plasmon polaritons. These phenomena are opposite to the widely known enhanced transparency of periodically modulated optically thick metal films. Our theoretical analysis can be a starting point for the experimental investigation of these intriguing phenomena.

cond-mat.other↗

arXiv2008

Resonance effects due to the excitation of surface Josephson plasma waves in layered superconductors

We analytically examine the excitation of surface Josephson plasma waves (SJPWs) in periodically-modulated layered superconductors. We show that the absorption of the incident electromagnetic wave can be substantially increased, for certain incident angles, due to the resonance excitation of SJPWs. The absorption increase is accompanied by the decrease of the specular reflection. Moreover, we find the physical conditions guaranteeing the total absorption (and total suppression of the specular reflection). These conditions can be realized for Bi2212 superconductor films.

cond-mat.supr-con↗

arXiv2007

Excitation of surface plasmon-polaritons in metal films with double periodic modulation: anomalous optical effects

We perform a thorough theoretical analysis of resonance effects when an arbitrarily polarized plane monochromatic wave is incident onto a double periodically modulated metal film sandwiched by two different transparent media. The proposed theory offers a generalization of the theory that had been build in our recent papers for the simplest case of one-dimensional structures to two-dimensional ones. A special emphasis is placed on the films with the modulation caused by cylindrical inclusions, hence, the results obtained are applicable to the films used in the experiments. We discuss a spectral composition of modulated films and highlight the principal role of ``resonance'' and ``coupling'' modulation harmonics. All the originating multiple resonances are examined in detail. The transformation coefficients corresponding to different diffraction orders are investigated in the vicinity of each resonance. We make a comparison between our theory and recent experiments concerning enhanced light transmittance and show the ways of increasing the efficiency of these phenomena. In the appendix we demonstrate a close analogy between ELT effect and peculiarities of a forced motion of two coupled classical oscillators.

cond-mat.other↗

arXiv2004

Variational principle for the relativistic hydrodynamic flows with discontinuities, and local invariants of motion

A rigorous method for introducing the variational principle describing relativistic ideal hydrodynamic flows with all possible types of discontinuities (including shocks) is presented in the framework of an exact Clebsch type representation of the four-velocity field as a bilinear combination of the scalar fields. The boundary conditions for these fields on the discontinuities are found. We also discuss the local invariants caused by the relabeling symmetry of the problem and derive recursion relations linking invariants of different types. These invariants are of specific interest for stability problems. In particular, we present a set of invariants based on the relativistic generalization of the Ertel invariant.

physics.flu-dyn↗

arXiv2004

Relativistic least action principle for discontinuous hydrodynamic flows, Hamiltonian variables, helicity and Ertel invariant

A rigorous method for introducing the variational principle describing relativistic ideal hydrodynamic flows with all possible types of breaks (including shocks) is presented in the framework of an exact Clebsch type representation of the four-velocity field as a bilinear combination of the scalar fields. The boundary conditions for these fields on the breaks are found. We also discuss the local invariants caused by the symmetries of the problem, including relabeling symmetry. In particular, the generalization of the well-known nonrelativistic Ertel invariant is presented.

physics.flu-dyn↗

arXiv2004

Canonical description of ideal magnetohydrodynamic flows and integrals of motion

In the framework of the variational principle the canonical variables describing ideal magnetohydrodynamic (MHD) flows of general type (i.e., with spatially varying entropy and nonzero values of all topological invariants) are introduced. The corresponding complete velocity representation enables us not only to describe the general type flows in terms of single-valued functions, but also to solve the intriguing problem of the ``missing'' MHD integrals of motion. The set of hitherto known MHD local invariants and integrals of motion appears to be incomplete: for the vanishing magnetic field it does not reduce to the set of the conventional hydrodynamic invariants. And if the MHD analogs of the vorticity and helicity were discussed earlier for the particular cases, the analog of Ertel invariant has been so far unknown. It is found that on the basis of the new invariants introduced a wide set of high-order invariants can be constructed. The new invariants are relevant both for the deeper insight into the problem of the topological structure of the MHD flows as a whole and for the examination of the stability problems. The additional advantage of the proposed approach is that it enables one to deal with discontinuous flows, including all types of possible breaks.

physics.flu-dyn↗

arXiv2003

Investigation of the spectra of coupled polaritons on the periodically modulated metallic layer and the narrow regions of anomalous transparency

The paper deals with the theoretical investigation of plane, normally incident electromagnetic wave transmission through the flat metal film whose dielectric constant has small periodical sinusoidal modulation in one dimension parallel to the projection of the electric field onto the film surface. The dependencies of the film transmittancy on the parameters of the problem (frequency, modulation depth and absorption) are examined. It is shown that the film transmittancy increases considerably when the conditions for resonance interaction of an incident electromagnetic wave with surface plasmon polaritons (SPPs) are met. It is found that for small but finite absorption there are two frequencies in the vicinity of which the transmittancy can achieve the values of the order of unity due to resonances on symmetric and antisymmetric (relative to the mean plane) SPP modes. It is shown that for each value of absorption there exists a certain optimal modulation depth, which maximizes the resonance transparency.

cond-mat↗

arXiv2002

Canonical description of ideal magnetohydrodynamics and integrals of motion

In the framework of the variational principle there are introduced canonical variables describing magnetohydrodynamic (MHD) flows of general type without any restrictions for invariants of the motion. It is shown that the velocity representation of the Clebsch type introduced by means of the variational principle with constraints is equivalent to the representation following from the generalization of the Weber transformation for the case of arbitrary MHD flows. The integrals of motion and local invariants for MHD are under examination. It is proved that there exists generalization of the Ertel invariant. It is expressed in terms of generalized vorticity field (discussed earlier by Vladimirov and Moffatt (V. A. Vladimirov, H. K. Moffatt, J. Fl. Mech., vol. 283, pp.~125--139, 1995) for the incompressible case). The generalized vorticity presents the frozen-in field for the barotropic and isentropic flows and therefore for these flows there exists generalized helicity invariant. This result generalizes one obtained by Vladimirov and Moffatt in the cited work for the incompressible fluid. It is shown that to each invariant of the conventional hydrodynamics corresponds MHD invariant and therefore our approach allows correct limit transition to the conventional hydrodynamic case. The additional advantage of the approach proposed enables one to deal with discontinuous flows, including all types of possible breaks.

physics.flu-dyn↗