Polarization effects in synchrotron radiation in strong magnetic field

The electron self-polarization effect is found to be more essential in comparison with quasi-classical approximation. The results of ultra-quantum and quasi-classical calculations for the photon polarization coincide with each other. The rigid correlation between the photon linear polarization and the electron spin is found

Electron-positron pair photo-production with radiation of a photon in magnetic field at nonresonant regime

Theoretical investigations of quantum electrodynamic processes in strong magnetic field are carried out. Such the processes may occur between colliding heavy ions. Magnetic fields of the nuclei are added and electric fields of nuclei mutually compensate one another in that region. The electron-positron pair production by a photon in the case when one additional photon is emitted in external magnetic field under nonresonant condition has been investigated. Kinematics of the process and the resonance conditions in approximation of strong magnetic field and weakly excited electron (positron) states (ultra-quantum approximation) have been studied. The resonant conditions have the place, when the photon energy is close to the splitting between Landau levels. The differential probability of nonresonant process has been obtained. The probability of the process is three order of magnitude less the resonant case.Проводятся теоретические исследования квантово-электродинамических процессов в сильном магнитном поле. Такие процессы могут происходить между сталкивающимися тяжелыми ионами. В этой области магнитные поля ядер складываются, а электрические поля взаимно компенсируются. Исследуется процесс рождения электрон-позитронной пары фотоном в случае, когда излучается один дополнительный фотон во внешнем магнитном поле при нерезонансных условиях. Изучаются кинематика процесса и условия резонанса в приближении сильного магнитного поля и слабо возбужденных состояний электронов (позитронов). Резонансные условия имеют место, когда энергия фотона близка к расстоянию между уровнями Ландау. Получена дифференциальная вероятность нерезонансного процесса в единицу времени. Вероятность такого процесса на три порядка меньше резонансного случая.Проводяться теоретичні дослідження квантово-електродинамічних процесів в сильному магнітному полі. Такі процеси можуть відбуватися при зіткненні важких іонів. В області між ними магнітні поля ядер складаються, а електричні поля взаємно компенсуються. Досліджується процес народження електрон-позитронної пари фотоном у випадку, коли випромінюється один додатковий фотон в зовнішньому магнітному полі при нерезонансних умовах. Вивчаються кінематика процесу і умови резонансу в наближенні сильного магнітного поля і слабо збуджених станів електронів (позитронів). Резонансні умови мають місце, коли енергія фотона близька до відстані між рівнями Ландау. Знайдено диференційну ймовірність нерезонансного процесу в одиницю часу. Ймовірність такого процесу на три порядки менша за резонансний випадок

Dicke superradiance on Landau levels

It is shown that in the inverted system of nonrelativistic electrons in rarefied magnetized plasma, when electron density on high Landau levels exceed some critical value defined by its transversal energy, magnetic field and temperature, the nonequilibrium phase transition occures with domain ordering of mutual orientations of interacting rotated dipoles. The intensity of cyclotron radiation of each domain in ordered phase becomes proportional to square of electron number in it

Photoproduction of the electron-positron pair with photon emission kinematics in strong magnetic field

The process of the photoproduction of the electron-positron pair with photon emission in strong magnetic field is studied. A kinematics of the process is investigated and threshold values of energies and momenta of particles are found.Розглядається процес фотонародження електрон-позитронної пари з випромінюванням фотона в сильному магнітному полі. Досліджено кінематику процесу і знайдено порогові значення енергій та імпульсів часток.Рассматривается процесс фоторождения электрон-позитронной пары с испусканием фотона в сильном магнитном поле. Исследована кинематика процесса и найдены пороговые значения энергий и импульсов частиц

Real-time thermal Schwinger-Dyson equation for quark self-energy in Landau gauge

By means of a formal expression of the Cornwall-Jackiw-Tomboulis effective potential for quark propagator at finite temperature and finite quark chemical potential, we derive the real-time thermal Schwinger-Dyson equation for quark propagator in Landau gauge. Denote the inverse quark propagator by $A(p^2)\not{p}-B(p^2)$, we argue that, when temperature $T$ is less than the given infrared momentum cutoff $p_c$, $A(p^2)=1$ is a feasible approximation and can be assumed in discussions of chiral symmetry phase transition problem in QCD.Comment: 8 pages, Latex, no figur

Ultimate gravitational mass defect

We present a new type of gravitational mass defect in which an infinite amount of matter may be bounded in a zero ADM mass. This interpolates between effects typical of closed worlds and T-spheres. We consider the Tolman model of dust distribution and show that this phenomenon reveals itself for a solution that has no origin on one side but is closed on the other side. The second class of examples corresponds to smooth gluing T-spheres to the portion of the Friedmann-Robertson-Walker solution. The procedure is generalized to combinations of smoothly connected T-spheres, FRW and Schwarzschild metrics. In particular, in this approach a finite T-sphere is obtained that looks for observers in two R-regions as the Schwarzschild metric with two different masses one of which may vanish.Comment: 9 pages. 1 reference added. To appear in Gen. Rel. Gra

Four-Body Chiral Order Parameters in the Massless Fermion Phase

The fermion four-point functions and condensates as the chiral symmetry order parameters are calculated analytically in U(1) gauge theory in the massless phase. It is shown that in leading order of the loop expansion of the effective action, there is a critical coupling for the nonperturbative parity-invariant chirality-changing four-fermion functions; this critical coupling however is the same as that for dynamical mass generation. Therefore there is no breaking of chiral symmetry through the condensation of four-fermion functions below the critical coupling for dynamical mass generation for the fermions.Comment: 28 pages and 1 postscript figure, REVTe

Wave function of the Universe in the early stage of its evolution

In quantum cosmological models, constructed in the framework of Friedmann-Robertson-Walker metrics, a nucleation of the Universe with its further expansion is described as a tunneling transition through an effective barrier between regions with small and large values of the scale factor $a$ at non-zero (or zero) energy. The approach for describing this tunneling consists of constructing a wave function satisfying an appropriate boundary condition. There are various ways for defining the boundary condition that lead to different estimates of the barrier penetrability and the tunneling time. In order to describe the escape from the tunneling region as accurately as possible and to construct the total wave function on the basis of its two partial solutions unambiguously, we use the tunneling boundary condition that the total wave function must represent only the outgoing wave at the point of escape from the barrier, where the following definition for the wave is introduced: the wave is represented by the wave function whose modulus changes minimally under a variation of the scale factor $a$. We construct a new method for a direct non-semiclassical calculation of the total stationary wave function of the Universe, analyze the behavior of this wave function in the tunneling region, near the escape point and in the asymptotic region, and estimate the barrier penetrability. We observe oscillations of modulus of wave function in the external region starting from the turning point which decrease with increasing of $a$ and which are not shown in semiclassical calculations. The period of such an oscillation decreases uniformly with increasing $a$ and can be used as a fully quantum dynamical characteristic of the expansion of the Universe.Comment: 19 pages, 21 files for 10 EPS figures, LaTeX svjour style. The Sec.2 (formalism of Wheeler-De Witt equation) is reduced. In Sec.3.1 definition of the outgoing wave from barrier is defined more accurately. In Sec.4.1 semiclassical calculations of wavew function and penetrability are performed and comparison with results in fully quantum approach is adde

Infrared cutoff dependence of the critical flavor number in three-dimensional QED

We solve, analytically and numerically, a gap equation in parity invariant QED_3 in the presence of an infrared cutoff \mu and derive an expression for the critical fermion number N_c as a function of \mu. We argue that this dependence of N_c on the infrared scale might solve the discrepancy between continuum Schwinger-Dyson equations studies and lattice simulations of QED_3.Comment: 5 pages, 1 figure (revtex4), final versio

Regularization-independent study of renormalized non-perturbative quenched QED

A recently proposed regularization-independent method is used for the first time to solve the renormalized fermion Schwinger-Dyson equation numerically in quenched QED$_4$. The Curtis-Pennington vertex is used to illustrate the technique and to facilitate comparison with previous calculations which used the alternative regularization schemes of modified ultraviolet cut-off and dimensional regularization. Our new results are in excellent numerical agreement with these, and so we can now conclude with confidence that there is no residual regularization dependence in these results. Moreover, from a computational point of view the regularization independent method has enormous advantages, since all integrals are absolutely convergent by construction, and so do not mix small and arbitrarily large momentum scales. We analytically predict power law behaviour in the asymptotic region, which is confirmed numerically with high precision. The successful demonstration of this efficient new technique opens the way for studies of unquenched QED to be undertaken in the near future.Comment: 20 pages,5 figure