137 research outputs found
Radiative Effects in the Standard Model Extension
The possibility of radiative effects induced by the Lorentz and CPT
non-invariant interaction term for fermions in the Standard Model Extension is
investigated. In particular, electron-positron photo-production and photon
emission by electrons and positrons are studied. The rates of these processes
are calculated in the Furry picture. It is demonstrated that the rates obtained
in the framework of the model adopted strongly depend on the polarization
states of the particles involved. As a result, ultra-relativistic particles
produced should occupy states with a preferred spin orientation, i.e., photons
have the sign of polarization opposite to the sign of the effective potential,
while charged particle are preferably in the state with the helicity coinciding
with the sign of the effective potential. This leads to evident spatial
asymmetries which may have certain consequences observable at high energy
accelerators, and in astrophysical and cosmological studies.Comment: 10 pages, 2 figures, Revtex4, to appear in Phys.Rev.D, misprints are
correcte
Effects of Vacuum Polarization in Strong Magnetic Fields with an Allowance Made for the Anomalous Magnetic Moments of Particles
Given the anomalous magnetic moments of electrons and positrons in the
one-loop approximation, we calculate the exact Lagrangian of an intense
constant magnetic field that replaces the Heisenberg-Euler Lagrangian in
traditional quantum electrodynamics (QED). We have established that the derived
generalization of the Lagrangian is real for arbitrary magnetic fields. In a
weak field, the calculated Lagrangian matches the standard Heisenberg-Euler
formula. In extremely strong fields, the field dependence of the Lagrangian
completely disappears, and the Lagrangian tends to a constant determined by the
anomalous magnetic moments of the particles.Comment: 19 pages, 3 figure
Beta decay and other processes in strong electromagnetic fields
We consider effects of the fields of strong electromagnetic waves on various
characteristics of quantum processes. After a qualitative discussion of the
effects of external fields on the energy spectra and angular distributions of
the final-state particles as well as on the total probabilities of the
processes (such as decay rates and total cross sections), we present a simple
method of calculating the total probabilities of processes with production of
non-relativistic charged particles. Using nuclear beta-decay as an example, we
study the weak and strong field limits, as well as the field-induced beta-decay
of nuclei stable in the absence of the external fields, both in the tunneling
and multi-photon regimes. We also consider the possibility of accelerating
forbidden nuclear beta-decays by lifting the forbiddeness due to the
interaction of the parent or daughter nuclei with the field of a strong
electromagnetic wave. It is shown that for currently attainable electromagnetic
fields all effects on total beta-decay rates are unobservably small.Comment: LaTeX, 30 pages, 2 figures. Invited contribution to the special issue
of Yadernaya Fizika dedicated to the centennial anniversary of birthday of
A.B. Migdal. V2: references adde
Scalar and Spinor Particles with Low Binding Energy in the Strong Stationary Magnetic Field Studied by Means of Two-and Three-Dimensional Models
On the basis of analytic solutions of Schrodinger and Pauli equations for a
uniform magnetic field and a single attractive -potential the
equations for the bound one-active electron states are discussed. It is vary
important that ground electron states in the magnetic field essentially
different from the analog state of spin-0 particles that binding energy has
been intensively studied at more then forty years ago. We show that binding
energy equations for spin-1/2 particles can be obtained without using of a
well-known language of boundary conditions in the model of -potential
that has been developed in pioneering works. Obtained equations are used for
the analytically calculation of the energy level displacements, which
demonstrate nonlinear dependencies on field intensities. It is shown that in a
case of the weak intensity a magnetic field indeed plays a stabilizing role in
considering systems. However the strong magnetic field shows the opposite
action. We are expected that these properties can be of importance for real
quantum mechanical fermionic systems in two- and three-dimensional cases.Comment: 18 page
Theory of the tau lepton anomalous magnetic moment
This article reviews and updates the Standard Model prediction of the tau
lepton g-2. Updated QED and electroweak contributions are presented, together
with new values of the leading-order hadronic term, based on the recent low
energy e+ e- data from BaBar, CMD-2, KLOE and SND, and of the hadronic
light-by-light contribution. The total prediction is confronted to the
available experimental bounds on the tau lepton anomaly, and prospects for its
future measurements are briefly discussed.Comment: 20 pages, 5 figure
Relativistic theory of inverse beta-decay of polarized neutron in strong magnetic field
The relativistic theory of the inverse beta-decay of polarized neutron, , in strong magnetic field is developed. For the proton
wave function we use the exact solution of the Dirac equation in the magnetic
filed that enables us to account exactly for effects of the proton momentum
quantization in the magnetic field and also for the proton recoil motion. The
effect of nucleons anomalous magnetic moments in strong magnetic fields is also
discussed. We examine the cross section for different energies and directions
of propagation of the initial neutrino accounting for neutrons polarization. It
is shown that in the super-strong magnetic field the totally polarized neutron
matter is transparent for neutrinos propagating antiparallel to the direction
of polarization. The developed relativistic approach can be used for
calculations of cross sections of the other URCA processes in strong magnetic
fields.Comment: 41 pages in LaTex including 11 figures in PostScript, discussion on
nucleons AMM interaction with magnetic field is adde
Electron-positron outflow from black holes
Gamma-ray bursts (GRBs) appear as the brightest transient phenomena in the
Universe. The nature of the central engine in GRBs is a missing link in the
theory of fireballs to their stellar mass progenitors. Here it is shown that
rotating black holes produce electron-positron outflow when brought into
contact with a strong magnetic field. The outflow is produced by a coupling of
the spin of the black hole to the orbit of the particles. For a nearly extreme
Kerr black hole, particle outflow from an initial state of electrostatic
equilibrium has a normalized isotropic emission of erg/s, where B is the
external magnetic field strength, B_c=4.4 x 10^{13}G, and M is the mass of the
black hole. This initial outflow has a half-opening angle
. A connection with fireballs in -ray bursts is
given.Comment: 10 pages LaTe
Propagation of axions in a strongly magnetized medium
The polarization operator of an axion in a degenerate gas of electrons
occupying the ground-state Landau level in a superstrong magnetic field G is investigated in a model with a
tree-level axion-electron coupling. It is shown that a dynamic axion mass,
which can fall within the allowed range of values , is generated under the conditions of strongly
magnetized neutron stars. As a result, the dispersion relation for axions is
appreciably different from that in a vacuum.Comment: RevTex, no figures, 13 pages, Revised version of the paper published
in J. Exp. Theor. Phys. {\bf 88}, 1 (1999
Dirac and Majorana neutrinos in matter
We consider the matter effects on neutrinos moving in background on the basis
of the corresponding quantum wave equations. Both Dirac and Majorana neutrino
cases are discussed. The effects for Dirac neutrino reflection and trapping as
well as neutrino-antineutrino annihilation and pair
creation in matter at the interface between two media with different densities
are considered. The spin light of neutrino in matter is also discussed.Comment: 11 pages, 2 figures, in: Proceedings of the 5th International
Conference on Non-Accelerator New Physics (Dubna, Russia, June 20-25, 2005).
V2: typos correcte
Photon emission by an ultra-relativistic particle channeling in a periodically bent crystal
This paper is devoted to a detailed analysis of the new type of the undulator
radiation generated by an ultra-relativistic charged particle channeling along
a crystal plane, which is periodically bent by a transverse acoustic wave, as
well as to the conditions limiting the observation of this phenomenon. This
mechanism makes feasible the generation of electromagnetic radiation, both
spontaneous and stimulated, emitted in a wide range of the photon energies,
from X- up to gamma-rays
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