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Papers by Vitaly Kocharovsky

Research paper thumbnail of Solitary high-Q resonance in a grating waveguide via parity symmetry breaking at mode crossing

Journal of Physics: Conference Series

A phenomenon of a solitary narrow high-Q resonance in a planar grating waveguide associated with ... more A phenomenon of a solitary narrow high-Q resonance in a planar grating waveguide associated with a bound state in the continuum (BIC) is revealed analytically. BICs appear when dispersion curves of the leaking even-parity and non-leaking odd-parity infinite-grating eigenmodes intersect. These intersections engender a parity symmetry break of the leaking eigenmode, causing it to decouple from a spatial Fourier harmonic that is emitted out of the waveguide. As a result, the otherwise low-Q waveguide eigenmode, comprised of those two aforementioned and some other infinite-grating eigenmodes, acquires a very high quality factor in a narrow vicinity of the mode-crossing frequency. Implementation of such a mechanism can be instructive for designing BICs in other photonic crystals and structures.

Research paper thumbnail of Solitary high-Q resonance in a grating waveguide via parity symmetry breaking at mode crossing

Journal of Physics: Conference Series

A phenomenon of a solitary narrow high-Q resonance in a planar grating waveguide associated with ... more A phenomenon of a solitary narrow high-Q resonance in a planar grating waveguide associated with a bound state in the continuum (BIC) is revealed analytically. BICs appear when dispersion curves of the leaking even-parity and non-leaking odd-parity infinite-grating eigenmodes intersect. These intersections engender a parity symmetry break of the leaking eigenmode, causing it to decouple from a spatial Fourier harmonic that is emitted out of the waveguide. As a result, the otherwise low-Q waveguide eigenmode, comprised of those two aforementioned and some other infinite-grating eigenmodes, acquires a very high quality factor in a narrow vicinity of the mode-crossing frequency. Implementation of such a mechanism can be instructive for designing BICs in other photonic crystals and structures.

Research paper thumbnail of Simultanious generation of pulse trains with different periods in a class C quantum-dot heterolaser

2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2021

Numerical simulations and qualitative analysis of the predicted simultaneous generation of differ... more Numerical simulations and qualitative analysis of the predicted simultaneous generation of different quasiperiodic pulse trains [1] - [3] in a CW multimode class C quantum-dot heterolaser with self-locking of some of the modes are carried out on the basis of the Maxwell-Bloch equations. For the class C lasers, a photon (cavity) lifetime is of the order of a lifetime of a polarization (a density of the quantum-dot optical dipoles). We consider the combined low-Q Fabry-Perot cavities with distributed feedback of counter-propagating waves, where higher-Q modes are situated close to the ends of a photonic bandgap and lower-Q quasi-equidistant modes occupy the adjacent wings.

Research paper thumbnail of Grand Canonical Versus Canonical Ensemble: Universal Structure of Statistics and Thermodynamics in a Critical Region of Bose–Einstein Condensation of an Ideal Gas in Arbitrary Trap

Journal of Statistical Physics, 2015

Research paper thumbnail of Dependence of the Lasing Spectrum and Self-Mode Locking on the Photonic Band Gap in Class-C Heterolasers with Distributed Feedback of Waves in a Fabry—Perot Cavity

Research paper thumbnail of Effects of self-Compton cooling on the synchrotron spectrum of GRBs

AIP Conference Proceedings, 2001

ABSTRACT We develope a self-consistent theory of the synchrotron-self-Compton emission for optica... more ABSTRACT We develope a self-consistent theory of the synchrotron-self-Compton emission for optically thin sources with a stationary injection of relativistic monoenergetic electrons. We investigate the electron distribution function, synchrotron and inverse Compton spectra and find their analytical asymptotics. The steady-state electron distribution entangled with synchrotron radiation via Compton losses is shown to produce spectral indices ranging from 1/2 to 1. Possible ways of addressing steep low-energy slopes in some bursts are pointed out. .

Research paper thumbnail of Cosmological gamma-ray bursts from collapse of a neutron star induced by a primordial black hole

Nuclear Physics B-proceedings Supplements - NUCL PHYS B-PROC SUPPL, 2000

Research paper thumbnail of Light Polarization and Linear Interaction of Screw Modes in Twisted Fiberswith Random Inhomogeneities

Research paper thumbnail of Weibel Mechanism of Magnetic-Field Generation in the Process of Expansion of a Collisionless-Plasma Bunch with Hot Electrons

Radiophysics and Quantum Electronics, 2020

Research paper thumbnail of Multi-scale magnetic field structures in an expanding elongated plasma cloud with hot electrons subject to an external magnetic field

We carry out 3D and 2D PIC-simulations of the expansion of a magnetized plasma that initially uni... more We carry out 3D and 2D PIC-simulations of the expansion of a magnetized plasma that initially uniformly fills a half-space and contains a semi-cylindrical region of heated electrons elongated along the surface of the plasma boundary. This geometry is related, for instance, to the ablation of a plane target by a femtosecond laser beam under quasi-cylindrical focusing. We find that the decay of the inhomogeneous plasma–vacuum discontinuity is strongly affected by an external magnetic field parallel to its boundary. We observe various transient phenomena, including the anisotropic scattering of electrons and the accompanying Weibel instability, and reveal various spatial structures of the arising magnetic field and current, including multiple flying apart filaments of a zpinch type and slowly evolving current sheets with different orientations. The magnitude of the self-generated magnetic field can be of the order of or significantly exceed that of the external one. Such phenomena are ...

Research paper thumbnail of Exact general solution to the three-dimensional Ising model and a self-consistency equation for the nearest-neighbors' correlations

We find an exact general solution to the three-dimensional (3D) Ising model via an exact self-con... more We find an exact general solution to the three-dimensional (3D) Ising model via an exact self-consistency equation for nearest-neighbors' correlations. It is derived by means of an exact solution to the recurrence equations for partial contractions of creation and annihilation operators for constrained spin bosons in a Holstein-Primakoff representation. In particular, we calculate analytically the total irreducible self-energy, the order parameter, the correlation functions, and the joined occupation probabilities of spin bosons. The developed regular microscopic quantum-field-theory method has a potential for a full solution of a long-standing and still open problem of 3D critical phenomena.

Research paper thumbnail of Bose–Einstein condensation in mesoscopic systems: The self-similar structure of the critical region and the nonequivalence of the canonical and grand canonical ensembles

Research paper thumbnail of Cyclotron line formation in the magnetized atmospheres of compact stars – I. The transfer equations for polarized radiation

Monthly Notices of the Royal Astronomical Society, 2016

Research paper thumbnail of A neutron star collapse induced by a primordial black hole as the source of cosmological γ-ray bursts

Radiophysics and Quantum Electronics, 1998

Research paper thumbnail of The influence of frequency redistribution on the transfer of gyroresonant photons in the atmospheres of compact stars: Monte-Carlo analysis

Radiophysics and Quantum Electronics, 2011

ABSTRACT We numerically model the frequency redistribution of gyroresonant photons in a plane-par... more ABSTRACT We numerically model the frequency redistribution of gyroresonant photons in a plane-parallel semi-infinite plasma atmosphere of a compact star by means of the Monte-Carlo method. We calculate the mean frequency shift and the mean number of scatterings for photons leaving the atmosphere as functions of the optical depth at emission, plasma temperature, and magnetic field strength. The probability of the escape of cyclotron-radiation photons from the atmosphere as a function of their optical depth at birth is calculated. The influence of the frequency redistribution effects on the spectrum of emergent radiation is studied.

Research paper thumbnail of On Dynamics of Relativistic Shock Waves with Losses in Gamma-Ray Burst Sources

Research paper thumbnail of Modeling of spectral features in the dynamic spectra of neutron stars

Radiophysics and Quantum Electronics, 2011

ABSTRACT Modeling of atomic and cyclotron lines in the emergent spectra of rotating neutron stars... more ABSTRACT Modeling of atomic and cyclotron lines in the emergent spectra of rotating neutron stars with various distributions of temperature over the star surface is carried out. General and special relativity effects are taken into account in the radiation transfer calculations. A novel method of analysis based on the Fourier series expansion of the observed spectra over rotation frequencies is proposed. It is shown that the mutual influence of the gravitational bending of light rays and rotation of the star leads to the formation of strong features (sometimes several features at once) in the Fourier-harmonic spectrum, whereas these features remain almost invisible in both the integrated and dynamic spectra. Possible application of the obtained results to the interpretation of absorption features in the spectrum of the single neutron star 1E 1207.4 − 5209 is discussed.

Research paper thumbnail of Towards an exact solution for the three-dimensional Ising model: A method of the recurrence equations for partial contractions

Physics Letters A, 2015

Abstract We find the exact solutions for the main steps in the analysis of the three-dimensional ... more Abstract We find the exact solutions for the main steps in the analysis of the three-dimensional Ising model. A method is based on a recently found rigorous theory of magnetic phase transitions in a mesoscopic lattice of spins, described as the constrained spin bosons in a Holstein–Primakoff representation.

Research paper thumbnail of Microscopic theory of phase transitions in a critical region

Research paper thumbnail of Relativistic jets in astrophysics

The properties of the plasma state of matter are determined by the motion and the electromagnetic... more The properties of the plasma state of matter are determined by the motion and the electromagnetic emission of the non-bound electrically charged particles --- electrons, positrons, protons and ions. It is not easy to create plasma in a laboratory. However this state is typical for the cosmic conditions --- at the stars and in the interstellar space. The properties of the laboratory as well as the space plasma are investigated at the Institute of Applied Physics of the Russian Academy of Sciences. The research is focused on the mechanisms of generation and propagation of the electromagnetic radiation --- from the radio waves to the gamma-rays --- in the planetary and stellar atmospheres and at the other astrophysical objects. The extreme physical conditions for a plasma are realized near the compact objects like black holes, neutron stars and collapsing nuclei of the massive stars. The plasma could be strongly non-equlibrium and can produce strong electromagnetic fields. Its bulk mot...

Research paper thumbnail of Solitary high-Q resonance in a grating waveguide via parity symmetry breaking at mode crossing

Journal of Physics: Conference Series

A phenomenon of a solitary narrow high-Q resonance in a planar grating waveguide associated with ... more A phenomenon of a solitary narrow high-Q resonance in a planar grating waveguide associated with a bound state in the continuum (BIC) is revealed analytically. BICs appear when dispersion curves of the leaking even-parity and non-leaking odd-parity infinite-grating eigenmodes intersect. These intersections engender a parity symmetry break of the leaking eigenmode, causing it to decouple from a spatial Fourier harmonic that is emitted out of the waveguide. As a result, the otherwise low-Q waveguide eigenmode, comprised of those two aforementioned and some other infinite-grating eigenmodes, acquires a very high quality factor in a narrow vicinity of the mode-crossing frequency. Implementation of such a mechanism can be instructive for designing BICs in other photonic crystals and structures.

Research paper thumbnail of Solitary high-Q resonance in a grating waveguide via parity symmetry breaking at mode crossing

Journal of Physics: Conference Series

A phenomenon of a solitary narrow high-Q resonance in a planar grating waveguide associated with ... more A phenomenon of a solitary narrow high-Q resonance in a planar grating waveguide associated with a bound state in the continuum (BIC) is revealed analytically. BICs appear when dispersion curves of the leaking even-parity and non-leaking odd-parity infinite-grating eigenmodes intersect. These intersections engender a parity symmetry break of the leaking eigenmode, causing it to decouple from a spatial Fourier harmonic that is emitted out of the waveguide. As a result, the otherwise low-Q waveguide eigenmode, comprised of those two aforementioned and some other infinite-grating eigenmodes, acquires a very high quality factor in a narrow vicinity of the mode-crossing frequency. Implementation of such a mechanism can be instructive for designing BICs in other photonic crystals and structures.

Research paper thumbnail of Simultanious generation of pulse trains with different periods in a class C quantum-dot heterolaser

2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2021

Numerical simulations and qualitative analysis of the predicted simultaneous generation of differ... more Numerical simulations and qualitative analysis of the predicted simultaneous generation of different quasiperiodic pulse trains [1] - [3] in a CW multimode class C quantum-dot heterolaser with self-locking of some of the modes are carried out on the basis of the Maxwell-Bloch equations. For the class C lasers, a photon (cavity) lifetime is of the order of a lifetime of a polarization (a density of the quantum-dot optical dipoles). We consider the combined low-Q Fabry-Perot cavities with distributed feedback of counter-propagating waves, where higher-Q modes are situated close to the ends of a photonic bandgap and lower-Q quasi-equidistant modes occupy the adjacent wings.

Research paper thumbnail of Grand Canonical Versus Canonical Ensemble: Universal Structure of Statistics and Thermodynamics in a Critical Region of Bose–Einstein Condensation of an Ideal Gas in Arbitrary Trap

Journal of Statistical Physics, 2015

Research paper thumbnail of Dependence of the Lasing Spectrum and Self-Mode Locking on the Photonic Band Gap in Class-C Heterolasers with Distributed Feedback of Waves in a Fabry—Perot Cavity

Research paper thumbnail of Effects of self-Compton cooling on the synchrotron spectrum of GRBs

AIP Conference Proceedings, 2001

ABSTRACT We develope a self-consistent theory of the synchrotron-self-Compton emission for optica... more ABSTRACT We develope a self-consistent theory of the synchrotron-self-Compton emission for optically thin sources with a stationary injection of relativistic monoenergetic electrons. We investigate the electron distribution function, synchrotron and inverse Compton spectra and find their analytical asymptotics. The steady-state electron distribution entangled with synchrotron radiation via Compton losses is shown to produce spectral indices ranging from 1/2 to 1. Possible ways of addressing steep low-energy slopes in some bursts are pointed out. .

Research paper thumbnail of Cosmological gamma-ray bursts from collapse of a neutron star induced by a primordial black hole

Nuclear Physics B-proceedings Supplements - NUCL PHYS B-PROC SUPPL, 2000

Research paper thumbnail of Light Polarization and Linear Interaction of Screw Modes in Twisted Fiberswith Random Inhomogeneities

Research paper thumbnail of Weibel Mechanism of Magnetic-Field Generation in the Process of Expansion of a Collisionless-Plasma Bunch with Hot Electrons

Radiophysics and Quantum Electronics, 2020

Research paper thumbnail of Multi-scale magnetic field structures in an expanding elongated plasma cloud with hot electrons subject to an external magnetic field

We carry out 3D and 2D PIC-simulations of the expansion of a magnetized plasma that initially uni... more We carry out 3D and 2D PIC-simulations of the expansion of a magnetized plasma that initially uniformly fills a half-space and contains a semi-cylindrical region of heated electrons elongated along the surface of the plasma boundary. This geometry is related, for instance, to the ablation of a plane target by a femtosecond laser beam under quasi-cylindrical focusing. We find that the decay of the inhomogeneous plasma–vacuum discontinuity is strongly affected by an external magnetic field parallel to its boundary. We observe various transient phenomena, including the anisotropic scattering of electrons and the accompanying Weibel instability, and reveal various spatial structures of the arising magnetic field and current, including multiple flying apart filaments of a zpinch type and slowly evolving current sheets with different orientations. The magnitude of the self-generated magnetic field can be of the order of or significantly exceed that of the external one. Such phenomena are ...

Research paper thumbnail of Exact general solution to the three-dimensional Ising model and a self-consistency equation for the nearest-neighbors' correlations

We find an exact general solution to the three-dimensional (3D) Ising model via an exact self-con... more We find an exact general solution to the three-dimensional (3D) Ising model via an exact self-consistency equation for nearest-neighbors' correlations. It is derived by means of an exact solution to the recurrence equations for partial contractions of creation and annihilation operators for constrained spin bosons in a Holstein-Primakoff representation. In particular, we calculate analytically the total irreducible self-energy, the order parameter, the correlation functions, and the joined occupation probabilities of spin bosons. The developed regular microscopic quantum-field-theory method has a potential for a full solution of a long-standing and still open problem of 3D critical phenomena.

Research paper thumbnail of Bose–Einstein condensation in mesoscopic systems: The self-similar structure of the critical region and the nonequivalence of the canonical and grand canonical ensembles

Research paper thumbnail of Cyclotron line formation in the magnetized atmospheres of compact stars – I. The transfer equations for polarized radiation

Monthly Notices of the Royal Astronomical Society, 2016

Research paper thumbnail of A neutron star collapse induced by a primordial black hole as the source of cosmological γ-ray bursts

Radiophysics and Quantum Electronics, 1998

Research paper thumbnail of The influence of frequency redistribution on the transfer of gyroresonant photons in the atmospheres of compact stars: Monte-Carlo analysis

Radiophysics and Quantum Electronics, 2011

ABSTRACT We numerically model the frequency redistribution of gyroresonant photons in a plane-par... more ABSTRACT We numerically model the frequency redistribution of gyroresonant photons in a plane-parallel semi-infinite plasma atmosphere of a compact star by means of the Monte-Carlo method. We calculate the mean frequency shift and the mean number of scatterings for photons leaving the atmosphere as functions of the optical depth at emission, plasma temperature, and magnetic field strength. The probability of the escape of cyclotron-radiation photons from the atmosphere as a function of their optical depth at birth is calculated. The influence of the frequency redistribution effects on the spectrum of emergent radiation is studied.

Research paper thumbnail of On Dynamics of Relativistic Shock Waves with Losses in Gamma-Ray Burst Sources

Research paper thumbnail of Modeling of spectral features in the dynamic spectra of neutron stars

Radiophysics and Quantum Electronics, 2011

ABSTRACT Modeling of atomic and cyclotron lines in the emergent spectra of rotating neutron stars... more ABSTRACT Modeling of atomic and cyclotron lines in the emergent spectra of rotating neutron stars with various distributions of temperature over the star surface is carried out. General and special relativity effects are taken into account in the radiation transfer calculations. A novel method of analysis based on the Fourier series expansion of the observed spectra over rotation frequencies is proposed. It is shown that the mutual influence of the gravitational bending of light rays and rotation of the star leads to the formation of strong features (sometimes several features at once) in the Fourier-harmonic spectrum, whereas these features remain almost invisible in both the integrated and dynamic spectra. Possible application of the obtained results to the interpretation of absorption features in the spectrum of the single neutron star 1E 1207.4 − 5209 is discussed.

Research paper thumbnail of Towards an exact solution for the three-dimensional Ising model: A method of the recurrence equations for partial contractions

Physics Letters A, 2015

Abstract We find the exact solutions for the main steps in the analysis of the three-dimensional ... more Abstract We find the exact solutions for the main steps in the analysis of the three-dimensional Ising model. A method is based on a recently found rigorous theory of magnetic phase transitions in a mesoscopic lattice of spins, described as the constrained spin bosons in a Holstein–Primakoff representation.

Research paper thumbnail of Microscopic theory of phase transitions in a critical region

Research paper thumbnail of Relativistic jets in astrophysics

The properties of the plasma state of matter are determined by the motion and the electromagnetic... more The properties of the plasma state of matter are determined by the motion and the electromagnetic emission of the non-bound electrically charged particles --- electrons, positrons, protons and ions. It is not easy to create plasma in a laboratory. However this state is typical for the cosmic conditions --- at the stars and in the interstellar space. The properties of the laboratory as well as the space plasma are investigated at the Institute of Applied Physics of the Russian Academy of Sciences. The research is focused on the mechanisms of generation and propagation of the electromagnetic radiation --- from the radio waves to the gamma-rays --- in the planetary and stellar atmospheres and at the other astrophysical objects. The extreme physical conditions for a plasma are realized near the compact objects like black holes, neutron stars and collapsing nuclei of the massive stars. The plasma could be strongly non-equlibrium and can produce strong electromagnetic fields. Its bulk mot...