868 research outputs found
Neutrino Geophysics at Baksan I: Possible Detection of Georeactor Antineutrinos
J.M. Herndon in 90-s proposed a natural nuclear fission georeactor at the
center of the Earth with a power output of 3-10 TW as an energy source to
sustain the Earth magnetic field. R.S. Raghavan in 2002 y. pointed out that
under certain condition antineutrinos generated in georeactor can be detected
using massive scintillation detectors. We consider the underground Baksan
Neutrino Observatory (4800 m.w.e.) as a possible site for developments in
Geoneutrino physics. Here the intrinsic background level of less than one
event/year in a liquid scintillation ~1000 target ton detector can be achieved
and the main source of background is the antineutrino flux from power reactors.
We find that this flux is ~10 times lower than at KamLAND detector site and two
times lower than at Gran Sasso laboratory and thus at Baksan the georeactor
hypothesis can be conclusively tested. We also discuss possible search for
composition of georector burning nuclear fuel by analysis of the antineutrino
energy spectrum.Comment: 7 pages in LaTeX, 3 PS figures, Submitted to Physics of Atomic Nucle
Interatomic potentials for the vibrational properties of III-V semiconductor nanostructures
We derive interatomic potentials for zinc blende InAs, InP, GaAs and GaP
semiconductors with possible applications in the realm of nanostructures. The
potentials include bond stretching interaction between the nearest and
next-nearest neighbors, a three body term and a long-range Coulomb interaction.
The optimized potential parameters are obtained by (i) fitting to bulk phonon
dispersions and elastic properties and (ii) constraining the parameter space to
deliver well behaved potentials for the structural relaxation and vibrational
properties of nanostructure clusters. The targets are thereby calculated by
density functional theory for clusters of up to 633 atoms. We illustrate the
new capability by the calculation Kleinman and Gr\"uneisen parameters and of
the vibrational properties of nanostructures with 3 to 5.5 nm diameter.Comment: 22 pages, 5 figures; Phys. Rev. B 201
Non-reciprocal light scattering by lattice of magnetic vortices
We report on experimental study of optical properties of two-dimensional
square lattice of triangle Co and CoFe nanoparticles with a vortex
magnetization distribution. We demonstrate that intensity of light scattered in
diffraction maxima depends on the vorticity of the particles magnetization and
it can be manipulated by applying an external magnetic field. The experimental
results can be understood in terms of phenomenological theory.Comment: 10 pages, 4 figure
Heavy Quarkonia in Quark-Gluon Plasma
Using the color-singlet free energy F_1 and total internal energy U_1
obtained by Kaczmarek et al. for a static quark Q and an antiquark Qbar in
quenched QCD, we study the binding energies and wave functions of heavy
quarkonia in a quark-gluon plasma. By minimizing the grand potential in a
simplified schematic model, we find that the proper color-singlet Q-Qbar
potential can be obtained from the total internal energy U_1 by subtracting the
gluon internal energy contributions. We carry out this subtraction in the local
energy-density approximation in which the gluon energy density can be related
to the local gluon pressure by the quark-gluon plasma equation of state. We
find in this approximation that the proper color-singlet Q-Qbar potential is
approximately F_1 for T ~ T_c and it changes to (3/4)F_1+(1/4)U_1 at high
temperatures. In this potential model, the J/psi is weakly bound above the
phase transition temperature T_c, and it dissociates spontaneously above 1.62
T_c, while chi_c and psi' are unbound in the quark-gluon plasma. The bottomium
states Upsilon, chi_b and Upsilon' are bound in the quark-gluon plasma and they
dissociate at 4.10 T_c, 1.18 T_c, and 1.38 T_c respectively. For comparison, we
evaluate the heavy quarkonium binding energies also in other models using the
free energy F_1 or the total internal energy U_1 as the Q-Qbar potential. The
comparison shows that the model with the new Q-Qbar potential proposed in this
manuscript gives dissociation temperatures that agree best with those from
spectral function analyses. We evaluate the cross section for
sigma(g+J/psi->c+cbar) and its inverse process, in order to determine the J/psi
dissociation width and the rate of J/psi production by recombining c and cbar
in the quark gluon plasma.Comment: 30 pages, in Late
Plasmon oscillations in ellipsoid nanoparticles: beyond dipole approximation
The plasmon oscillations of a metallic triaxial ellipsoid nanoparticle have
been studied within the framework of the quasistatic approximation. A general
method has been proposed for finding the analytical expressions describing the
potential and frequencies of the plasmon oscillations of an arbitrary
multipolarity order. The analytical expressions have been derived for an
electric potential and plasmon oscillation frequencies of the first 24 modes.
Other higher orders plasmon modes are investigated numerically.Comment: 33 pages, 12 figure
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