50,153 research outputs found
Radiation generated by accelerating and rotating charged black holes in (anti-)de Sitter space
Asymptotic behaviour of gravitational and electromagnetic fields of exact
type D solutions from the large Plebanski-Demianski family of black hole
spacetimes is analyzed. The amplitude and directional structure of radiation is
evaluated in cases when the cosmological constant is non-vanishing, so that the
conformal infinities have either de Sitter-like or anti-de Sitter-like
character. In particular, explicit relations between the parameters that
characterize the sources (that is their mass, electric and magnetic charges,
NUT parameter, rotational parameter, and acceleration) and properties of the
radiation generated by them are presented. The results further elucidate the
physical interpretation of these solutions and may help to understand radiative
characteristics of more general spacetimes than those that are asymptotically
flat.Comment: 24 pages, 18 figures. To appear in Classical and Quantum Gravit
Bias Voltage and Temperature Dependence of Hot Electron Magnetotransport
We present a qualitative model study of energy and temperature dependence of
hot electron magnetotransport. This model calculations are based on a simple
argument that the inelastic scattering strength of hot electrons is strongly
spin and energy dependent in the ferromagnets. Since there is no clear
experimental data to compare with this model calculations, we are not able to
extract clear physics from this model calculations. However, interestingly this
calculations display that the magnetocurrent increases with bias voltage
showing high magnetocurrent if spin dependent imaginary part of proper self
energy effect has a substantial contribution to the hot electron
magnetotransport. Along with that, the hot electron magnetotransport is
strongly influence by the hot electron spin polarization at finite
temperatures
Mass Terms in Effective Theories of High Density Quark Matter
We study the structure of mass terms in the effective theory for
quasi-particles in QCD at high baryon density. To next-to-leading order in the
expansion we find two types of mass terms, chirality conserving
two-fermion operators and chirality violating four-fermion operators. In the
effective chiral theory for Goldstone modes in the color-flavor-locked (CFL)
phase the former terms correspond to effective chemical potentials, while the
latter lead to Lorentz invariant mass terms. We compute the masses of Goldstone
bosons in the CFL phase, confirming earlier results by Son and Stephanov as
well as Bedaque and Sch\"afer. We show that to leading order in the coupling
constant there is no anti-particle gap contribution to the mass of
Goldstone modes, and that our results are independent of the choice of gauge.Comment: 22 pages, 4 figure
Meissner screening mass in two-flavor quark matter at nonzero temperature
We calculate the Meissner screening mass of gluons 4--7 in two-flavor quark
matter at nonzero temperature. To this end, we study the effective potential of
the 2SC/g2SC phases including a vector condensate . We find
that the Meissner mass becomes real at the critical temperature which is about
the half of the chemical potential mismatch. The phase diagram of the neutral
two-flavor color superconductor is presented in the plane of temperature and
coupling strength. We indicate the unstable region for gluons 4--7 on the phase
diagram.Comment: 4 pages, 3 figures, minor revisions to text, version to appear in PR
Zero Temperature Chiral Phase Transition in (2+1)-Dimensional QED with a Chern-Simons Term
We investigate the zero temperature chiral phase transition in
(2+1)-dimensional QED in the presence of a Chern-Simons term, changing the
number of fermion flavors. In the symmetric phase, there are no light degrees
of freedom even at the critical point. Unlike the case without a Chern-Simons
term, the phase transition is first-order.Comment: 7 pages, RevTeX, no figure
Synthesis and structural characterization of 2Dioxane.2H2O.CuCl2: metal-organic compound with Heisenberg antiferromagnetic S=1/2 chains
A novel organometallic compound 2Dioxane.CuCl2.2H2O has been synthesized and
structurally characterized by X-ray crystallography. Magnetic susceptibility
and zero-field inelastic neutron scattering have also been used to study its
magnetic properties. It turns out that this material is a weakly coupled
one-dimensional S=1/2 Heisenberg antiferromagnetic chain system with chain
direction along the crystallographic c axis and the nearest-neighbor
intra-chain exchange constant J=0.85(4) meV. The next-nearest-neighbor
inter-chain exchange constant J' is also estimated to be 0.05 meV. The observed
magnetic excitation spectrum from inelastic neutron scattering is in excellent
agreement with numerical calculations based on the Muller ansatz.Comment: 4 pages; 5 figure
Mission Analysis Program for Solar Electric Propulsion (MAPSEP). Volume 2: User's manual
A user's manual which describes input/output routines and recommended operating procedures relating to MAPSEP is presented. Samples runs are included
Mission Analysis Program for Solar Electric Propulsion (MAPSEP). Volume 1: Analytical manual
The mission analysis program for solar electric propulsion (MAPSEP) is comprised of the basic modes: TOPSEP (trajectory generation), GODSEP (linear error analysis), and SIMSEP (simulation). The program is designed to analyze any low thrust mission with respect to trajectory performance, guidance and navigation, and to provide system related requirements for the purpose of vehicle design. The MAPSEP organization is described along with all models and algorithms. Topics discussed include: trajectory and error covariance propagation methods, orbit determination processes, thrust modeling, and trajectory correction (guidance) schemes
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