arXiv subjects

Pavel A. Andreev

Publications and source records attributed to Pavel A. Andreev.

At least 37 records · Page 2Linked to original sources

arXiv2021

Spin-electron-acoustic waves and solitons in high-density degenerate relativistic plasmas

The spin-electron-acoustic waves (sometimes called the spin-plasmons) can be found in degenerate electron gas if the spin-up electrons and spin down electrons move relatively each other. Here, we suggest relativistic hydrodynamics with the separate spin evolution which allows us to study linear and nonlinear spin-electron-acoustic waves, including the spin-electron-acoustic solitons. Presented hydrodynamic model is the corresponding generalization of the relativistic hydrodynamic model with the average reverse gamma factor evolution which consists of the equations for evolution of the following functions the partial concentrations (for spin-up electrons and spin down electrons), the partial velocity fields, the partial average reverse relativistic gamma factors, and the partial flux of the reverse relativistic gamma factors. We find that the relativistic effects decreases the phase velocity of spin-electron-acoustic waves. Numerical analysis of the changes of spectra of Langmuir wave, spin-electron-acoustic wave, and ion-acoustic wave under the change of the spin polarization of electrons is presented. It is demonstrated that spectra of Langmuir wave and spin-electron-acoustic wave getting closer to each other in the relativistic limit. Spin dependence of the amplitude and width of the relativistic spin-electron-acoustic soliton is demonstrated as well. Reformation of the bright soliton of potential of the electric field into the dark soliton under the influence of the relativistic effects is found.

physics.plasm-ph↗

arXiv2021

On the structure of relativistic hydrodynamics for hot plasmas

Novel structure for relativistic hydrodynamics of classic plasmas is derived following the microscopic dynamics of charged particles. The derivation is started from the microscopic definition of concentration. Obviously, the concentration evolution leads to the continuity equation and gives the definition of particle current. Introducing no arbitrary functions, we consider the evolution of current (which does not coincide with the momentum density). It leads to a set of new function which, to the best of our knowledge, have not been consider in the literature earlier. One of these functions is the average reverse relativistic (gamma) factor. Its current is also considered as one of basic functions. Evolution of new functions appears via the concentration and particle current so the set of equations partially closes itself. Other functions are presented as functions of basic function as a part of truncation presiger. Two pairs of chosen functions construct two four vectors. Evolution of these four vectors leads to appearance of two four tensors which are considered instead of the energy-momentum tensor. The Langmuir waves are considered within the suggested model.

physics.plasm-ph↗

arXiv2021

Relativistic hydrodynamic model with the average reverse gamma factor evolution for the degenerate plasmas: high-density ion-acoustic solitons

High-density low-temperature plasmas with degenerate species are considered in the limit of high Fermi velocities close to the speed of light. The small amplitude ion-acoustic solitons are studied in this regime. Presented analysis is based on the relativistic hydrodynamic model with the average reverse gamma factor evolution consists of the equations for evolution of the following functions the concentration, the velocity field, the average reverse relativistic gamma factor, and the flux of the reverse relativistic gamma factor, which are considered as main hydrodynamic variables. Justification of the suggested model via comparison of the hydrodynamic results with the result of application of the relativistic Vlasov kinetic equation is made in the linear approximation.

physics.plasm-ph↗

arXiv2021

Anisotropic pressure effects in hydrodynamic description of waves propagating parallel to the magnetic field in relativistically hot plasmas

The structure of novel hydrodynamic model of plasmas with the relativistic temperatures consisted of four equations for the material fields is presented for the regime of anisotropic pressure and other tensors describing the thermal effects. Presented model constructed of equation for evolution of the concentration, the velocity field, the average reverse relativistic $γ$ functor, and the flux of the reverse relativistic $γ$ functor, which are considered as main hydrodynamic variables. Four pressure-like tensors (two second rank tensors and one fourth rank tensor) describe the thermal effects. Among them we have the flux of the particle current and the current of the flux of the reverse relativistic $γ$ functor. The high-frequency excitations are considered analytically in order to trace the contribution of the anisotropy of pressure-like tensors in their spectra.

physics.plasm-ph↗

arXiv2021

Microscopic model for relativistic hydrodynamics of ideal plasmas

Relativistic hydrodynamics of classic plasmas is derived from the microscopic model in the limit of ideal plasmas. The chain of equations is constructed step by step starting from the concentration evolution. It happens that the energy density and the momentum density do not appear at such approach, but new relativistic-hydrodynamic variables appear in the model. These variables has no nonrelativistic analogs, but they are reduced to the concentration, the particle current, the pressure (the flux of the particle current) if relativistic effects are dropped. These variables are reduced to functions of the concentration, the particle current, the pressure if the thermal velocities are dropped in compare with the relativistic velocity field. Final equations are presented in the monopole limit of the meanfield (the selfconsistent field) approximation. Hence, the contributions of the electric dipole moment, magnetic dipole moment, electric quadrupole moment, etc of the macroscopically infinitesimal element of volume appearing in derived equations are dropped.

physics.plasm-ph↗

arXiv2021

A hydrodynamic model of Alfvenic waves and fast magneto-sound in the relativistically hot plasmas at propagation parallel to the magnetic field

The Alfvenic waves and fast magneto-sound in the relativistically hot plasmas are considered. This study is based on the novel hydrodynamic model of plasmas with the relativistic temperatures consisted of four equations for the material fields: the concentration and the velocity field \emph{and} the average reverse relativistic $γ$ functor and the flux of the reverse relativistic $γ$ functor. Three temperature regimes giving considerably different behavior of the spectrum of Alfvenic waves are found. Four temperature regimes are obtained for the fast magneto-sound. All these regimes show considerable variations from the nonrelativistic regime. Dispersion equations for the electromagnetic transverse wave propagating parallel to the external magnetic field are found analytically. Their small frequency solutions are analyzed numerically.

physics.plasm-ph↗

arXiv2021

On a hydrodynamic description of waves propagating perpendicular to the magnetic field in relativistically hot plasmas

The novel hydrodynamic model of plasmas with the relativistic temperatures consisted of four equations for the material fields: the concentration and the velocity field \emph{and} the average reverse relativistic $γ$ functor and the flux of the reverse relativistic $γ$ functor is applied to study high-frequency part of spectrum of electromagnetic waves propagating perpendicular to the external magnetic field. The thermal effects considered for the temperatures close to the rest energy of electrons considerably change the dispersion equation in compare with the nonrelativistic temperatures. Analytical analysis of the changes is presented.

physics.plasm-ph↗

arXiv2021

Grey solitons in the ultracold fermions at the full spin polarization

A minimal coupling quantum hydrodynamic model of spin-1/2 fermions at the full spin polarization corresponding to a nonlinear Schrodinger equation is considered. The nonlinearity is primarily caused by the Fermi pressure. It provides an effective repulsion between fermions. However, there is the additional contribution of the short-range interaction appearing in the third order by the interaction radius. It leads to the modification of the pressure contribution. Solitons are considered for the infinite medium with no restriction on the amplitude of the wave. The Fermi pressure leads to the soliton in form of the area of decreased concentration. However, the center of solution corresponding to the area of minimal concentration has nonzero value of concentration. Therefore, the grey soliton is found. Soliton exist if the speed of its propagation is below the Fermi velocity.

cond-mat.quant-gas↗

arXiv2021

Hydrodynamic model of skyrmions and vorticities in the spin-1 Bose-Einstein condensate in ferromagnetic phase at finite temperatures

Quantum hydrodynamic of skyrmions in spinor ultracold bosons at the finite temperature is described. The limit regime of BEC appearing at the zero temperature is discussed either. The skyrmions are found as the solution of the spin evolution equation for the ferromagnetic phase of spin-1 ultracold bosons. It is demonstrated that the quantum part of the spin current gives major contribution in the formation of the skyrmions. The interplay between the quantum (spin) vorticity and the classic vorticity is considered for the finite temperatures. Bosons are presented as two fluids associated with the Bose-Einstein condensate and the normal fluid. All effects are considered for the ferromagnetic phase.

cond-mat.quant-gas↗

arXiv2021

Quantum hydrodynamics of the spinor Bose-Einstein condensate at non-zero temperatures

Finite temperature hydrodynamic model is derived for the spin-1 ultracold bosons by the many-particle quantum hydrodynamic method. It is presented as the two fluid model of the BEC and normal fluid. The linear and quadratic Zeeman effects are included. Scalar and spin-spin like short-range interactions are considered in the first order by the interaction radius. It is also represented as the set of two nonlinear Pauli equations. The spectrum of the bulk collective excitations is considered for the ferromagnetic phase in the small temperature limit. The spin wave is not affected by the presence of the small temperature in the described minimal coupling model, where the thermal part of the spin-current of the normal fluid is neglected. The two sound waves are affected by the spin evolution in the same way as the change of spectrum of the single sound wave in BEC, where speed of sound is proportional to $g_{1}+g_{2}$ with $g_{i}$ are the interaction constants.

cond-mat.quant-gas↗

arXiv2021

Two-fluid hydrodynamics of cold atomic bosons under influence of the quantum fluctuations at non-zero temperatures

Ultracold Bose atoms is the physical system, where the quantum and nonlinear phenomena play crucial role. Ultracold bosons are considered at the small finite temperatures. Bosons are considered as two different fluids: Bose-Einstein condensate and normal fluid (the thermal component). An extended hydrodynamic model is obtained for both fluids, where the pressure evolution equations and the pressure flux third rank tensor evolution equations are considered along with the continuity and Euler equations. It is found that the pressure evolution equation contains zero contribution of the short-range interaction. The pressure flux evolution equation contains the interaction which gives the quantum fluctuations in the zero temperature limit. Here, we obtain its generalization for the finite temperature. The contribution of interaction in the pressure flux evolution equation which goes to zero in the zero temperature limit is found. The model is obtained via the straightforward derivation from the microscopic many-particle Schrodinger equation in the coordinate representation.

cond-mat.quant-gas↗

arXiv2020

Novel soliton in dipolar BEC caused by the quantum fluctuations

Solitons in the extended hydrodynamic model of the dipolar Bose-Einstein condensate with quantum fluctuations are considered. This model includes the continuity equation for the scalar field of concentration, the Euler equation for the vector field of velocity, the pressure evolution equation for the second rank tensor of pressure, and the evolution equation for the third rank tensor. Large amplitude soliton solution caused by the dipolar part of quantum fluctuations is found. It appears as the bright soliton. Hence, it is the area of compression of the number of particles. Moreover, it exists for the repulsive short-range interaction.

cond-mat.quant-gas↗

arXiv2020

Hydrodynamics of the atomic Bose-Einstein condensate beyond the mean-field approximation: a mini-review

Several hydrodynamic models the atomic Bose-Einstein condensate beyond the mean-field approximation are discussed together from one point of view. All these models are derived from microscopic quantum description. The derivation is made within the many-particle quantum hydrodynamics method suggested by L. Kuz'menkov. The derivation is demonstrated and discussed for the mean-field regime revealing the Gross-Pitaevskii equation as the simplest illustration. It appears in the first order by the interaction radius. Generalization of the hydrodynamic Euler equation obtained in the third order by the interaction radius are discussed. It includes the contribution of the isotropic short-range interaction presented by the third space derivative of the square of concentration. The Euler equation also includes the contribution of the anisotropic part of the short-range interaction proportional to the second order spherical function. Systematic account of the quantum fluctuations in terms of the many-particle quantum hydrodynamics method requires the extension of the set of hydrodynamic equations from the couple continuity and Euler equations to the set of four equations which also includes the pressure evolution equation and the evolution equation for the third rank analog of pressure. The pressure evolution equation contains no interaction contribution in the first order by the interaction radius. The source of the quantum fluctuations is in the interaction caused term in the third rank tensor evolution equation which is obtained in the first order by the interaction radius.

cond-mat.quant-gas↗

arXiv2020

Hydrodynamics of quantum corrections to the Coulomb interaction via the third rank tensor evolution equation: Application to the Langmuir waves and the spin-electron-acoustic waves

If we study the quantum effects in plasmas in terms of traditional hydrodynamics via the continuity and Euler equations we find the quantum Bohm potential and the force of spin-spin interaction. However, if we extend the set hydrodynamic equations beyond the 13-moments approximation, and include the third rank tensor evolution equation along with the pressure evolution equation, we obtain the quantum corrections to the Coulomb interaction. It is found in contrast with the fact that hydrodynamic equations for the higher rank tensors do not contain interaction in the classic plasmas studied in the selfconsistent (meanfield) approximation. Therefore, we present the quantum hydrodynamic model, where the quantum effects are studied beyond the quantum Bohm potential. Developed model is considered in two regimes: all electrons in plasmas are considered as the single fluid, and the separate spin evolution regime, where electrons with different spin projections are considered as two different fluids. To illustrate the fundamental meaning of found quantum effects we demonstrate their contribution in the spectrum of the Langmuir waves and the spin-electron-acoustic waves. It is worth to mention that the application of the pressure evolution equation ensures that the contribution of pressure in the Langmuir wave spectrum is proportional to $(3/5)v_{Fe}^{2}$, unlike $(1/3)v_{Fe}^{2}$ appearing from hydrodynamics based on the continuity and Euler equations, where $v_{Fe}$ is the Fermi velocity. Same correction corresponds on other plasmas phenomena like the speed of sound for spin-electron-acoustic waves. Moreover, it is found that novel quantum effects provide the novel wave solutions.

physics.plasm-ph↗

arXiv2020

Quantum hydrodynamic theory of quantum fluctuations in dipolar Bose-Einstein condensate

Traditional quantum hydrodynamics of Bose-Einstein condensates (BECs) is restricted by the continuity and Euler equations. It corresponds to the well-known Gross-Pitaevskii equation. However, the quantum Bohm potential, which is a part of the momentum flux, has a nontrivial part with can evolve under the quantum fluctuations. To cover this phenomenon in terms of hydrodynamic methods we need to derive equations for the momentum flux, and the third rank tensor. In all equations we consider the main contribution of the short-range interaction (SRI) in the first order by the interaction radius. Derived hydrodynamics consists of four hydrodynamic equations. The third moment evolution equation contains interaction leading to the quantum fluctuations. It includes new interaction constant. The Gross-Pitaevskii interaction constant is the integral of potential, but the second interaction constant is the integral of second derivative of potential. If we have dipolar BECs we deal with a long-range interaction. Its contribution is proportional to the potential of dipole-dipole interaction (DDI). The Euler equation contains the derivative of the potential. The third rank tensor evolution equation contains the third derivative of the potential. The quantum fluctuations lead to existence of the second wave solution. Moreover, the quantum fluctuations introduce the instability of BECs. If the DDI is attractive, but being smaller then the repulsive SRI presented by the first interaction constant, there is the long-wavelength instability. For the repulsive DDI these is more complex picture. There is the small area with the long-wavelength instability which transits into stability interval, where two waves exist. There is the short-wavelength instability as well. These results are found for the DDI strength comparable with the Gross-Pitaevskii SRI.

cond-mat.quant-gas↗

arXiv2020

Bosonic bright soliton in the mixture of repulsive Bose-Einstein condensate and polarized ultracold fermions under influence of the pressure evolution

Repulsive Bose-Einstein condensate, where the short-range interaction is included up to the third order by the interaction radius, demonstrates existence of a bright soliton in a narrow interval of parameters. This soliton is studied here for the boson-fermion mixture, where spin-1/2 fermions are consider in the regime of full spin polarization. Influence of fermions via the boson-fermion interaction is considered up to the third order by the interaction radius. Fermions themselves are considered by hydrodynamic model including the pressure evolution equation. Interaction between fermions is considered. The first order by the interaction radius gives zero contribution in the Euler equation and the pressure evolution equation, but the third order by the interaction radius provides nonzero contributions in both equations. Repulsive (attractive) boson-fermion interaction leads to the bright (dark) fermionic soliton.

cond-mat.quant-gas↗

arXiv2020

Extended hydrodynamics of the degenerate partially spin polarized fermions with the short-range interaction up to the third order by the interaction radius approximation

A possibility of the hydrodynamic description of ultracold fermions via the microscopic derivation of the model is described. Differently truncated hydrodynamic models are derived and compared. All models are based on the microscopic many-particle Schrödinger equation. Minimal coupling model based on the continuity and Euler equations are considered. The extended hydrodynamic model including the independent dynamics of the momentum flux (the pressure evolution) is derived. Influence of the spin polarization is described. The short-range interaction is considered in the isotropic limit. The interaction is considered up to the third order by the interaction radius. Therefore, the single fluid model of spin-1/2 fermions and the two fluid model of spin-1/2 fermions are under consideration in this paper. Spectra of bulk collective excitations are derived and compared in terms of different models.

cond-mat.quant-gas↗

arXiv2019

On the interaction constant measurement of polarized fermions via sound wave spectra obtained from hydrodynamics with the pressure evolution equation

Usually, hydrodynamic equations are restricted by the continuity and Euler equations. However, the account of the higher moments of the distribution function gives better description of the kinetic properties. Therefore, the pressure tensor evolution equation (PTEE) is derived for spin polarized degenerate fermions. Moreover, it is found that the pressure tensor enters the interaction term generalizing the p-wave interaction in the Euler equation. Hence, the PTEE allows to give a more accurate description of the interaction in Euler equation. Next, the interaction is calculated for the PTEE. The developed model is applied to the small amplitude bulk collective excitations in homogeneous and trapped fermions in order to suggest the methods of experimental measurement of the interaction constant of polarized fermions. It is demonstrated that the anisotropy in the momentum space revealing in the difference of the pressures in the anisotropy direction and the perpendicular directions leads to a method of detection of the interaction constant.

cond-mat.quant-gas↗