6,293 research outputs found
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
On CY-LG correspondence for (0,2) toric models
We conjecture a description of the vertex (chiral) algebras of the (0,2)
nonlinear sigma models on smooth quintic threefolds. We provide evidence in
favor of the conjecture by connecting our algebras to the cohomology of a
twisted chiral de Rham sheaf. We discuss CY/LG correspondence in this setting.Comment: 25 pages, reference added, typos corrected, to be published in
Advances in Mathematic
Rare semileptonic meson decays in R-parity violating MSSM
We discuss rare meson decays and () in a supersymmetric
extension of the Standard Model with R-parity violation. Estimates of the
branching ratios for these decays are presented.Comment: 5 pages, 1 figure; title modified to better reflect the contents, a
normalization error corrected for D-meson decays, modifying parts of Table 1;
a reference and DESY Report number added; to appear in the Proceedings of the
12th. Lomonosov Conference on Elementary Particle Physics, Moscow State
University, Moscow, Russia, 25-31 August 200
Bilinear R-parity Violation in Rare Meson Decays
We discuss rare meson decays and () in a supersymmetric
extension of the standard model with explicit breaking of R-parity by bilinear
Yukawa couplings in the superpotential. Estimates of the branching ratios for
these decays are given. We also compare our numerical results with analogous
ones previously obtained for two other mechanisms of lepton number violation:
exchange by massive Majorana neutrinos and trilinear R-parity violation.Comment: 5 pages, 1 figure; To appear in the Proceedings of the 13th Lomonosov
Conference on Elementary Particle Physics, 23 -- 29 August, 2007, Moscow,
Russi
Homogenization of the planar waveguide with frequently alternating boundary conditions
We consider Laplacian in a planar strip with Dirichlet boundary condition on
the upper boundary and with frequent alternation boundary condition on the
lower boundary. The alternation is introduced by the periodic partition of the
boundary into small segments on which Dirichlet and Neumann conditions are
imposed in turns. We show that under the certain condition the homogenized
operator is the Dirichlet Laplacian and prove the uniform resolvent
convergence. The spectrum of the perturbed operator consists of its essential
part only and has a band structure. We construct the leading terms of the
asymptotic expansions for the first band functions. We also construct the
complete asymptotic expansion for the bottom of the spectrum
Lepton pair production by high-energy neutrino in an external electromagnetic field
The process of the lepton pair production by a neutrino propagating in an
external electromagnetic field is investigated in the framework of the Standard
Model. Relatively simple exact expression for the probability as the single
integral is obtained, which is suitable for a quantitative analysis.Comment: 9 pages, LATEX, 2 PS figures, submitted to Modern Physics Letters
Spectral and localization properties of the Dirichlet wave guide with two concentric Neumann discs
Bound states of the Hamiltonian describing a quantum particle living on three
dimensional straight strip of width are investigated. We impose the Neumann
boundary condition on the two concentric windows of the radii and
located on the opposite walls and the Dirichlet boundary condition on the
remaining part of the boundary of the strip. We prove that such a system
exhibits discrete eigenvalues below the essential spectrum for any .
When and tend to the infinity, the asymptotic of the eigenvalue is
derived. A comparative analysis with the one-window case reveals that due to
the additional possibility of the regulating energy spectrum the anticrossing
structure builds up as a function of the inner radius with its sharpness
increasing for the larger outer radius. Mathematical and physical
interpretation of the obtained results is presented; namely, it is derived that
the anticrossings are accompanied by the drastic changes of the wave function
localization. Parallels are drawn to the other structures exhibiting similar
phenomena; in particular, it is proved that, contrary to the two-dimensional
geometry, at the critical Neumann radii true bound states exist.Comment: 25 pages, 7 figure
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