2,541 research outputs found
The effect of two-temperature post-shock accretion flow on the linear polarization pulse in magnetic cataclysmic variables
The temperatures of electrons and ions in the post-shock accretion region of
a magnetic cataclysmic variable (mCV) will be equal at sufficiently high mass
flow rates or for sufficiently weak magnetic fields. At lower mass flow rates
or in stronger magnetic fields, efficient cyclotron cooling will cool the
electrons faster than the electrons can cool the ions and a two-temperature
flow will result. Here we investigate the differences in polarized radiation
expected from mCV post-shock accretion columns modeled with one- and
two-temperature hydrodynamics. In an mCV model with one accretion region, a
magnetic field >~30 MG and a specific mass flow rate of ~0.5 g/cm/cm/s, along
with a relatively generic geometric orientation of the system, we find that in
the ultraviolet either a single linear polarization pulse per binary orbit or
two pulses per binary orbit can be expected, depending on the accretion column
hydrodynamic structure (one- or two-temperature) modeled. Under conditions
where the physical flow is two-temperature, one pulse per orbit is predicted
from a single accretion region where a one-temperature model predicts two
pulses. The intensity light curves show similar pulse behavior but there is
very little difference between the circular polarization predictions of one-
and two-temperature models. Such discrepancies indicate that it is important to
model some aspect of two-temperature flow in indirect imaging procedures, like
Stokes imaging, especially at the edges of extended accretion regions, were the
specific mass flow is low, and especially for ultraviolet data.Comment: Accepted for publication in Astrophysics & Space Scienc
BES3 time of flight monitoring system
A Time of Flight monitoring system has been developed for BES3.
The light source is a 442-443 nm laser diode, which is stable and provides a
pulse width as narrow as 50 ps and a peak power as large as 2.6 W. Two
optical-fiber bundles with a total of 512 optical fibers, including spares, are
used to distribute the light pulses to the Time of Flight counters. The design,
operation, and performance of the system are described.Comment: 8 pages 16 figures, submitted to NI
Instantons of Type IIB Supergravity in Ten Dimensions
A family of SO(10) symmetric instanton solutions in Type IIB supergravity is
developed. The instanton of least action is a candidate for the low-energy,
semiclassical approximation to the {D=--1} brane. Unlike a previously published
solution,[GGP] this admits an interpretation as a tunneling amplitude between
perturbatively degenerate asymptotic states, but with action twice that found
previously. A number of associated issues are discussed such as the relation
between the magnetic and electric pictures, an inversion symmetry of the
dilaton and the metric, the topology of the background, and some
properties of the solution in an "instanton frame" corresponding to a
Lagrangian in which the dilaton's kinetic energy vanishes.Comment: 15 pages, no figures; Version 2 has revised sections IV and V.
Earlier equations are essentially unchanged, but interpretation changed, on
advice of counse
Distributed phase-covariant cloning with atomic ensembles via quantum Zeno dynamics
We propose an interesting scheme for distributed orbital state quantum
cloning with atomic ensembles based on the quantum Zeno dynamics. These atomic
ensembles which consist of identical three-level atoms are trapped in distant
cavities connected by a single-mode integrated optical star coupler. These
qubits can be manipulated through appropriate modulation of the coupling
constants between atomic ensemble and classical field, and the cavity decay can
be largely suppressed as the number of atoms in the ensemble qubits increases.
The fidelity of each cloned qubit can be obtained with analytic result. The
present scheme provides a new way to construct the quantum communication
network.Comment: 5 pages, 4 figure
Exclusion statistics: A resolution of the problem of negative weights
We give a formulation of the single particle occupation probabilities for a
system of identical particles obeying fractional exclusion statistics of
Haldane. We first derive a set of constraints using an exactly solvable model
which describes an ideal exclusion statistics system and deduce the general
counting rules for occupancy of states obeyed by these particles. We show that
the problem of negative probabilities may be avoided with these new counting
rules.Comment: REVTEX 3.0, 14 page
Fractional Exclusion Statistics and Anyons
Do anyons, dynamically realized by the field theoretic Chern-Simons
construction, obey fractional exclusion statistics? We find that they do if the
statistical interaction between anyons and anti-anyons is taken into account.
For this anyon model, we show perturbatively that the exchange statistical
parameter of anyons is equal to the exclusion statistical parameter. We obtain
the same result by applying the relation between the exclusion statistical
parameter and the second virial coefficient in the non-relativistic limit.Comment: 9 pages, latex, IFT-498-UN
Traveling wave solutions for a predator-prey system with Sigmoidal response function
We study the existence of traveling wave solutions for a diffusive
predator-prey system. The system considered in this paper is governed by a
Sigmoidal response function which is more general than those studied
previously. Our method is an improvement to the original method introduced in
the work of Dunbar \cite{Dunbar1,Dunbar2}. A bounded Wazewski set is used in
this work while unbounded Wazewski sets were used in \cite{Dunbar1,Dunbar2}.
The existence of traveling wave solutions connecting two equilibria is
established by using the original Wazewski's theorem which is much simpler than
the extended version in Dunbar's work
Superconductivity and single crystal growth of Ni0:05TaS2
Superconductivity was discovered in a Ni0:05TaS2 single crystal. A Ni0:05TaS2
single crystal was successfully grown via the NaCl/KCl flux method. The
obtained lattice constant c of Ni0:05TaS2 is 1.1999 nm, which is significantly
smaller than that of 2H-TaS2 (1.208 nm). Electrical resistivity and
magnetization measurements reveal that the superconductivity transition
temperature of Ni0:05TaS2 is enhanced from 0.8 K (2H-TaS2) to 3.9 K. The
charge-density-wave transition of the matrix compound 2H-TaS2 is suppressed in
Ni0:05TaS2. The success of Ni0:05TaS2 single crystal growth via a NaCl/KCl flux
demonstrates that NaCl/KCl flux method will be a feasible method for single
crystal growth of the layered transition metal dichalcogenides.Comment: 13pages, 6 figures, Published in SS
Exclusion Statistics of Quasiparticles in Condensed States of Composite Fermion Excitations
The exclusion statistics of quasiparticles is found at any level of the
hierarchy of condensed states of composite fermion excitations (for which
experimental indications have recently been found). The hierarchy of condensed
states of excitations in boson Jain states is introduced and the statistics of
quasiparticles is found. The quantum Hall states of charged -anyons
( -- the exclusion statistics parameter) can be described as
incompressible states of -anyons ( -- an even number).Comment: 4 page
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