253 research outputs found
Electrically neutral Dirac particles in the presence of external fields: exact solutions
In the present article we present exact solutions of the Dirac equation for
electric neutral particles with anomalous electric and magnetic moments. Using
the algebraic method of separation of variables, the Dirac equation is
separated in cartesian, cylindrical and spherical coordinates, and exact
solutions are obtained in terms of special functions.Comment: 20pp, IVIC-CFLE-93/02 (this is a version without Tex problems, the
first version was corrupted
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
Neutrino spin oscillations in gravitational fields
We study neutrino spin oscillations in gravitational fields. The
quasi-classical approach is used to describe the neutrino spin evolution. First
we examine the case of a weak gravitational field. We obtain the effective
Hamiltonian for the description of neutrino spin oscillations. We also receive
the neutrino transition probability when a particle propagates in the
gravitational field of a rotating massive object. Then we apply the general
technique to the description of neutrino spin oscillations in the Schwarzschild
metric. The neutrino spin evolution equation for the case of the neutrino
motion in the vicinity of a black hole is obtained. The effective Hamiltonian
and the transition probability are also derived. We examine the neutrino
oscillations process on different circular orbits and analyze the frequencies
of spin transitions. The validity of the quasi-classical approach is also
considered.Comment: RevTeX4, 9 pages, 1 esp figure; article was revised, some misprints
were corrected, 6 references added; accepted for publication in
Int.J.Mod.Phys.
Modification of Coulomb law and energy levels of the hydrogen atom in a superstrong magnetic field
We obtain the following analytical formula which describes the dependence of
the electric potential of a point-like charge on the distance away from it in
the direction of an external magnetic field B: \Phi(z) = e/|z| [ 1-
exp(-\sqrt{6m_e^2}|z|) + exp(-\sqrt{(2/\pi) e^3 B + 6m_e^2} |z|) ]. The
deviation from Coulomb's law becomes essential for B > 3\pi B_{cr}/\alpha = 3
\pi m_e^2/e^3 \approx 6 10^{16} G. In such superstrong fields, electrons are
ultra-relativistic except those which occupy the lowest Landau level (LLL) and
which have the energy epsilon_0^2 = m_e^2 + p_z^2. The energy spectrum on which
LLL splits in the presence of the atomic nucleus is found analytically. For B >
3 \pi B_{cr}/\alpha, it substantially differs from the one obtained without
accounting for the modification of the atomic potential.Comment: version to be published in Physical Review D (incorrect "Keywords" in
previous version have been cancelled
Quantum treatment of neutrino in background matter
Motivated by the need of elaboration of the quantum theory of the spin light
of neutrino in matter (), we have studied in more detail the exact
solutions of the Dirac equation for neutrinos moving in the background matter.
These exact neutrino wavefunctions form a basis for a rather powerful method of
investigation of different neutrino processes in matter, which is similar to
the Furry representation of quantum electrodynamics in external fields. Within
this method we also derive the corresponding Dirac equation for an electron
moving in matter and consider the electromagnetic radiation ("spin light of
electron in matter", ) that can be emitted by the electron in this case.Comment: 10 pages, in: Proceedings of QFEXT'05 (The Seventh Workshop on
Quantum Field Theory under the Influence of External Conditions, IEEC, CSIC
and University of Barcelona, Barcelona, Catalonia, Spain, 5-9 September
2005.), ed. by Emilio Elizalde and Sergei Odintsov; published in Journal of
Physics
The bremsstrahlung equation for the spin motion in LHC
The influence of the bremsstrahlung on the spin motion is expressed by the
equation which is the analogue and generalization of the
Bargmann-Michel-Telegdi equation. The new constant is involved in this
equation. This constant can be immediately determined by the experimental
measurement of the spin motion, or it follows from the classical limit of
quantum electrodynamics with radiative corrections.Comment: 9 page
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
Chiral density waves in quark matter within the Nambu--Jona-Lasinio model in an external magnetic field
A possibility of formation of static dual scalar and pseudoscalar density
wave condensates in dense quark matter is considered for the
Nambu--Jona-Lasinio model in an external magnetic field. Within a mean-field
approximation, the effective potential of the theory is obtained and its minima
are numerically studied; a phase diagram of the system is constructed. It is
shown that the presence of a magnetic field favors the formation of spatially
inhomogeneous condensate configurations at low temperatures and arbitrary
non-zero values of the chemical potential.Comment: 13 pages, 4 figure
Interaction of Radiation and a Relativistic Electron in Motion in a Constant Magnetic Field
The work examines the effect of multiple photon emission on the quantum
mechanical state of an electron emitting synchrotron radiation and on the
intensity of that radiation. Calculations are done with the variant of
perturbation theory based on the use of extended coherent states. A general
formula is derived for the number of emitted photons, which allows for taking
into account their mutual interaction. A model problem is used to demonstrate
the absence of the infrared catastrophe in the modified perturbation theory.
Finally, the electron density matrix is calculated, and the analysis of this
matrix makes it possible to conclude that the degree of the elecron's spatial
localization increases with the passage of time if the electron is being
accelerated.Comment: 29 pages, no figure
- …