Electron self-energy in a magnetic field

In the lowest order in the fine-structure constant, the electron self-energy in an external magnetic field can be written in the form of a double integral representation containing the exact information about the radiative shift and width of the energy levels, without approximation in the field strength. In the low-field expansion of the radiative shift, the leading term is conveniently interpreted in terms of the electron's anomalous magnetic moment, whilst in very strong fields the enhancement of the cyclotron motion makes the shift a positive, slowly increasing function of the field intensity. It follows that, even in superstrong magnetic fields, the electromagnetic interaction cannot give rise to an instability of the electron-positron vacuum.     

Axion self-energy in a magnetic field

The axion self-energy in an external magnetic field is investigated. It is shown that, in addition to the standard contribution due to axion interaction with virtual fermions, there exists the contribution induced by photon exchange. For the two contributions, expressions that take exactly into account an external field are obtained, and the limit of an ultrastrong magnetic field is explored for them. The question of whether two-dimensional QED, which effectively arises in the limit of a strong magnetic field, is applicable to calculating the virtual-fermion-induced contribution to the axion self-energy is analyzed.     

Electron self-energy in nonlocal field theory

In the framework of quantum electrodynamics with the nonlocal interaction it is shown that the correspondence principle holds in the problem on the self-mass of an electron and a particle with arbitrary spin. It appears that the second order of perturbation theory in the limit ? → 0 gives just the classical expression for the electron self-energy, and all higher order corrections are zero.     

Electron scattering by a short-range potential in a constant homogeneous magnetic field

The scattering of spin-oriented electrons, moving in a constant homogeneous magnetic field, by a short-range potential is analyzed. The change in the electron spin orientation is calculated using the Born approximation.     

Electron self-energy in the presence of a magnetic field: hyperfine splitting and g factor

A high-precision numerical calculation is reported for the self-energy correction to the hyperfine splitting and to the bound-electron g factor in hydrogenlike ions with low nuclear charge numbers. The binding nuclear Coulomb field is treated to all orders, and the nonperturbative remainder beyond the known Zalpha-expansion coefficients is determined. For the 3He+ ion, the nonperturbative remainder yields a contribution of -450 Hz to the normalized difference of the 1S and 2S hyperfine-structure intervals, to be compared with the experimental uncertainty of 71 Hz and with the theoretical error of 50 Hz due to other contributions. In the case of the g factor, the calculation provides the most stringent test of equivalence of the perturbative and nonperturbative approaches reported so far in the bound-state QED calculations.     

Electron on a cylinder with topological defects in a homogeneous magnetic field

In this work we study the effects of the geometry and topology of a cylinder on the energy levels of an electron moving in a homogeneous magnetic field. We consider the existence of topological defects as a screw dislocation and a disclination. When we take the region of movement as the full cylindrical surface, we find that, by increasing the strength of the screw dislocation, the dispersion on the electronic energy levels is affected and monotonically increasing. For an electron moving in an almost flat region we show that the dispersion on the Landau levels decrease monotonically as we increase the strength of the screw dislocation. The lowest Landau level can reach a zero value, leaving the energy of the system solely given by the geometry of the cylinder, which does not depend on the magnetic field. In both situations, as we change the deficit angle of the disclination, we observe that the energy levels are shifted and the magnitude of such shift depends on the magnetic field. The Landau levels for a flat sample are recovered in the limit of an infinite cylinder radius.     

Electron transport across a microconstriction in an arbitrarily oriented homogeneous magnetic field

An analysis is made of ballistic electron transport in three-dimensional microconstrictions of elliptic cross section located in an arbitrarily oriented magnetic field. The model of a parabolic confinement potential is used to obtain and analyze the dependence of hybrid frequencies on the magnitude and direction of the magnetic field. An expansion of the conductance as a Fourier series is obtained and used to study Aharonov-Bohm and Shubnikov-de Haas oscillations as a function of the field and the stepped quantization structure of the conductance. A possible explanation is given for the experimentally observed effect of conductance quantization at fairly high temperatures.     

Spin-1 particle in a homogeneous magnetic field

The Corben-Schwinger theory gives imaginary values of the energy, forS ₃ ² =1 states, in very intensive magnetic fields. The theory proposed by the author, which is most satisfactory in the nonrelativistic approximation, does not have this defect forS ₃ ² =1 states, but it appears forS ₃ ² =0 states.     

Generation of squeezed states in a homogeneous magnetic field

It is shown that a homogeneous magnetic field acting on a charged harmonic oscillator in the ground state may produce a state with reduced fluctuation of one of the quadrature phase amplitudes. The amount of squeezing in the final state depends on the time during which the magnetic field was switched on.     

Quasiclassical distribution function of electrons in a homogeneous magnetic field

Vlasov's equation is used to find the classical nonrelativistic and relativistic distribution functions that describe an electron beam of bounded radius in a homogeneous magnetic field. In the quasiclassical approximation, by means of the exact wave functions of an electron in a homogeneous magnetic field, the quantum relativistic distribution function with allowance for the electron spin is found. The mean physical quantities that characterize the radially bounded electron beam are found as functions of the temperature and electron spin.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 50–56, July, 1976.It is a pleasant duty to thank Professor V. G. Bagrov for discussing the results.     

Electron self-energy and effective mass in a single heterostructure

In this paper, we investigate the electron self-energy and effective mass in a single heterostructure using Greenfunction method. Numerical calculations of the electron self-energy and effective mass for GaAs/A1As heterostructure are performed. The results show that the self-energy (effective mass) of electrons, which incorporate the energy of electron coupling to interface-optical phonons and half of the three-dimensional longitudinal optical phonons, increase (decrease) monotonically from that of interface polaron to that of the 3D bulk polaron with increasing the distance between the positions of the electron and interface.     

Absence of the efimov effect in a homogeneous magnetic field

A system of three identical particles in a homogeneous magnetic field is studied. It is shown that the Hamiltonian of this system with short-range potentials after the separation of the center of mass motion has a finite discrete spectrum for each fixed type m of the rotational (SO(2)) symmetry.Supported by the Erwin Schrödinger Institute, Austria, International Science Foundation Grant No. 9400 and Russian Grant of the State Committee for High Education RF-94-27-1022.     

Interplay between a homogeneous magnetic field and an antiferromagnetic field in one-dimensional superconductors

Mean-field theory applied to superconductors with one-dimensional band in the presence of both the homogeneous magnetic field H₀ and the antiferromagnetic field H_Q, the second-order phase transition temperature is investigated for the arbitrary angle θ between H₀ and H_Q. It is found that the remarkable superconducting region in the case of θ = 0 is retained only for small θ and that the spatially dependent order parameter coexists with the spatially uniform order parameter except for θ = τ/2.     

Crossed diagram contribution to the electron self-energy due to impurity scattering in a magnetic field

We consider the contribution of crossed diagrams to the self-energy for a system of free electrons and fixed point impurities in the presence of a strong magnetic field. At the peaks of the Shubnikov-de Haas (S.d.H.) oscillations the dependence on the impurity concentration of the crossed diagram is the same as in the generalized Born approximation (n _i ^2/3 ). Nevertheless, for the S.d.H. regime the contribution of the crossed diagrams is shown to be unimportant.     

Electron heat transport measured in a stochastic magnetic field

New profile measurements have allowed the electron thermal diffusivity profile to be estimated from power balance in the Madison Symmetric Torus where magnetic islands overlap and field lines are stochastic. The measurements show that (1) the electron energy transport is conductive not convective, (2) the measured thermal diffusivities are in good agreement with numerical simulations of stochastic transport, and (3) transport is greatly reduced near the reversal surface where magnetic diffusion is small.     

Electron beam dose distribution in a solenoid magnetic field

The results of simulation of irradiation of tissue-equivalent targets by 20-MeV electron beams in the presence of solenoid magnetic fields are discussed. These results are compared with the corresponding data obtained without magnetic fields. The data obtained can be used to solve beam therapy problems.     

Cherenkov radiation: Electron self-energy approach

A short review is given of a previous paper on Cherenkov radiation (CR) by Fülöp and Biró (1992), together with some aspects of the collective dipole oscillations of atomic microclusters (atomic analog of the nuclear giant resonance). Finally, the CR energy loss of a relativistic charged particle in matter is obtained by evaluating the self-energy of the particle in the medium.     

Excitons in a homogeneous magnetic field: A modified perturbation approach

We propose a specially adapted perturbational scheme to calculate the energies and weve functions of excitons in a homogeneous magnetic fieldB. The strength ofB is arbitrary. In contrast to involved variational calculations, our final results are entirely analytical and may serve as a starting point for further applications. As for the energies, we find good agreement with previous work. Moreover we show that the well-known small-B and large-B asymptotics for the exact eigenvalues areboth contained in our unifying formulas as limiting cases.