arXiv subjects

I. D. Feranchuk

Publications and source records attributed to I. D. Feranchuk.

28 records · Page 2Linked to original sources

arXiv2014

Justification of the single-mode approximation for a finite-duration laser pulse interacting with an electron

The interaction Hamiltonian of an electron and a quasi-monochromatic pulse of a strong quantized electromagnetic field is examined. Canonical transformations of the field variables are found that allow the division of the system's Hamiltonian in two parts. The first one describes the interaction between an electron and a single collective mode of the field. The properties of this mode are defined by the superposition of the modes corresponding to the pulse wave packet. The second part describes the field fluctuations relatively to the collective mode. The field intensity, pulse duration and transversal spread are estimated for which a single-mode approximation can be used for the system's description.

quant-ph↗

arXiv2014

Regularization of the vacuum fluctuation energy in quantum electrodynamics

It is shown that the total energy of the vacuum fluctuations of the electron-positron and electromagnetic fields in the quantum electrodynamics can be equal to zero if the "bare" electron charge is chosen by adequate way. The value of "bare" electron charge calculated from this condition proves to be in a qualitative agreement with that one which was found independently from the solution of the "physical electron" problem.

physics.gen-ph↗

arXiv2013

Collapse-and-revival dynamics of strongly laser-driven electrons

The relativistic quantum dynamics of an electron in an intense single-mode quantized electromagnetic field is investigated with special emphasis on the spin degree of freedom. In addition to fast spin oscillations at the laser frequency, a second time scale is identified due to the intensity dependent emissions and absorptions of field quanta. In analogy to the well-known phenomenon in atoms at moderate laser intensity, we put forward the conditions of collapses and revivals for the spin evolution in laser-driven electrons starting at feasible $10^{18}$ W/cm$^2$.

physics.atom-ph↗

arXiv2006

Soliton-like excitation in large-alpha QED

The nonperturbative analysis of the one-particle excitation of the electron-positron field is made in the paper. The standard form of quantum electrodynamics (QED) is used but the coupling constant $α_0$ is supposed to be of a large value ($α_0 \gg 1$). It is shown that in this case the quasi-particle excitation can be produced together with the non-zero scalar component of the electromagnetic field. Self-consistent equations for spatially localized charge distribution coupled with an electromagnetic field are derived. Soliton-like solution with a nonzero charge for these equations are calculated numerically. The solution proves to be unique if the coupling constant is fixed. It leads to the condition of charge quantization if the non-overlapping $n$-soliton states are considered. It is also proved that the dispersion law of the soliton-like excitation is consistent with Lorentz invariance of the QED equations.

math-ph↗

arXiv2005

New solution for the polaron problem

New variational ansatz for the large-radius Fröhlich polaron is considered. The corresponding operator estimation for the energy of polaron proves to be very similar to the result found by Feynman on the basis of the variational principle for the functional integral of the system. It allows us to make clear the problem of ``phase transition'' and to anylize the structure of the localized state of the polaron in the intermediate coupling regime. It is shown that the analogous state exists also for the model of particle-field interaction with the divergent perturbation theory.

cond-mat.str-el↗

arXiv2005

Experiments with Parametric X-Ray Radiation (PXR) from Non-Relativistic Electrons

Interaction of non-relativistic electrons with single crystal target may produce coherent x-rays. That is the result of interference between two known x-ray generation mechanisms having orientational behavior, namely parametric x-rays and coherent {\it Bremsstrahlung}. Experiments aimed to PXR research were performed with 50-100 keV electrons and its distinctive features were observed. Requirements to the experimental set-up, detector instrumental response, and targets as well as experiment geometry are discussed in detail. Series of PXR spectra in various conditions were recorded and their distinctive features were observed. Tuning of radiation frequency with crystal-target rotation was observed for the first time for low energy electrons. Dependence of the x-ray frequency on the beam energy was detected. Soft PXR peak with energy below 1 keV was observed for the first time. Possible applications of PXR for structure analysis and crystallography are discussed. These results are obtained in the framework of ISTC project {#}B626

physics.ins-det↗

arXiv2004

Operator Method for Nonperturbative Calculation of the Thermodynamic Values in Quantum Statistics. Diatomic Molecular Gas

Operator method and cumulant expansion are used for nonperturbative calculation of the partition function and the free energy in quantum statistics. It is shown for Boltzmann diatomic molecular gas with some model intermolecular potentials that the zeroth order approximation of the proposed method interpolates the thermodynamic values with rather good accuracy in the entire range of both the Hamiltonian parameters and temperature. The systematic procedure for calculation of the corrections to the zeroth order approximation is also considered.

quant-ph↗

arXiv2004

Regularization of the Coulomb scattering problem

Exact solutions of the Schrödinger equation for the Coulomb potential are used in the scope of both stationary and time-dependent scattering theories in order to find the parameters which define regularization of the Rutherford cross-section when the scattering angle tends to zero but the distance r from the center remains fixed. Angular distribution of the particles scattered in the Coulomb field is investigated on the rather large but finite distance r from the center. It is shown that the standard asymptotic representation of the wave functions is not available in the case when small scattering angles are considered. Unitary property of the scattering matrix is analyzed and the "optical" theorem for this case is discussed. The total and transport cross-sections for scattering of the particle by the Coulomb center proved to be finite values and are calculated in the analytical form. It is shown that the considered effects can be essential for the observed characteristics of the transport processes in semiconductors which are defined by the electron and hole scattering in the fields of the charged impurity centers.

quant-ph↗

arXiv2003

Realization of the anomalous scattering method in crystallography on the basis of the parametric X-ray radiation

Spectra of parametric X-ray radiation (PXR) are considered in the range of anomalous dispersion for one of the atoms in a crystal elementary cell. The PXR spectra are calculated both for the ultra-relativistic and non-relativistic electrons for the specific conditions corresponding to the organic compounds . It is shown that analysis of the RXR angular distribution permits one to realize the method of anomalous scattering for direct measurement of the phases of structure amplitudes without additional isomorphic intrusion of a heavy atom.

cond-mat.mtrl-sci↗

arXiv2003

Nonperturbative Description Of The Mass And Charge Renormalization In Quantum Electrodynamics

In this paper the nonperturbative analysis of the spectrum for one-particle excitations of the electron-positron field (EPF) is considered in the paper. A standard form of the quantum electrodynamics (QED) is used but the charge of the "bare" electron $e_0$ is supposed to be of a large value. It is shown that in this case the quasi-particle can be formed with a non-zero averaged value of the scalar component of the electromagnetic field (EMF). Self-consistent equations for the distribution of charge density in the "physical" electron (positron) are derived. A variational solution of these equations is obtained and it defines the finite renormalization of the charge and mass of the electron (positron). It is found that the coupling constant between EPF and EMF and mass of the "bare" electron can be connected with the observed values of the fine structure constant and the mass of the "physical" electron. It is also shown that although the non-renormalized QED corresponds to the strong coupling between EPF and EMF, the interaction between "physical" electron (positron) with EMF is defined by the observed value of the coupling constant. It is proved that the translational motion of the "physical" particle is separated from its internal degrees of freedom. As a result the dependence of the one-particle excitation energy on its total momentum corresponds to the relativistic spectrum of a free particle with the observed value of mass. Regularization of the terms of a series of the perturbation theory is due to the form-factor of the "physical" electron (positron).

hep-th↗