23,098 research outputs found
Ground State Energy for Fermions in a 1D Harmonic Trap with Delta Function Interaction
Conjectures are made for the ground state energy of a large spin 1/2 Fermion
system trapped in a 1D harmonic trap with delta function interaction. States
with different spin J are separately studied. The Thomas-Fermi method is used
as an effective test for the conjecture.Comment: 4 pages, 3 figure
Exploration of Resonant Continuum and Giant Resonance in the Relativistic Approach
Single-particle resonant-states in the continuum are determined by solving
scattering states of the Dirac equation with proper asymptotic conditions in
the relativistic mean field theory (RMF). The regular and irregular solutions
of the Dirac equation at a large radius where the nuclear potentials vanish are
relativistic Coulomb wave functions, which are calculated numerically.
Energies, widths and wave functions of single-particle resonance states in the
continuum for ^{120}Sn are studied in the RMF with the parameter set of NL3.
The isoscalar giant octupole resonance of ^{120}Sn is investigated in a fully
consistent relativistic random phase approximation. Comparing the results with
including full continuum states and only those single-particle resonances we
find that the contributions from those resonant-states dominate in the nuclear
giant resonant processes.Comment: 16 pages, 2 figure
A coproduct structure on the formal affine Demazure algebra
In the present paper we generalize the coproduct structure on nil Hecke rings
introduced and studied by Kostant-Kumar to the context of an arbitrary
algebraic oriented cohomology theory and its associated formal group law. We
then construct an algebraic model of the T-equivariant oriented cohomology of
the variety of complete flags.Comment: 28 pages; minor revision of the previous versio
Parity Violation in Neutrino Transport and the Origin of Pulsar Kicks
In proto-neutron stars with strong magnetic fields, the neutrino-nucleon
scattering/absorption cross sections depend on the direction of neutrino
momentum with respect to the magnetic field axis, a manifestation of parity
violation in weak interactions. We study the deleptonization and thermal
cooling (via neutrino emission) of proto-neutron stars in the presence of such
asymmetric neutrino opacities. Significant asymmetry in neutrino emission is
obtained due to multiple neutrino-nucleon scatterings. For an ordered magnetic
field threading the neutron star interior, the fractional asymmetry in neutrino
emission is about , corresponding to a pulsar kick velocity
of about km/s for a total radiated neutrino energy of
erg.Comment: AASTeX, 10 pages including 2 ps figures; ApJ Letter in press (March
10, 1998). Shortened to agree with the published versio
Optimal queue-size scaling in switched networks
We consider a switched (queuing) network in which there are constraints on
which queues may be served simultaneously; such networks have been used to
effectively model input-queued switches and wireless networks. The scheduling
policy for such a network specifies which queues to serve at any point in time,
based on the current state or past history of the system. In the main result of
this paper, we provide a new class of online scheduling policies that achieve
optimal queue-size scaling for a class of switched networks including
input-queued switches. In particular, it establishes the validity of a
conjecture (documented in Shah, Tsitsiklis and Zhong [Queueing Syst. 68 (2011)
375-384]) about optimal queue-size scaling for input-queued switches.Comment: Published in at http://dx.doi.org/10.1214/13-AAP970 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
The effect of different baryons impurities
We demonstrate the different effect of different baryons impurities on the
static properties of nuclei within the framework of the relativistic mean-field
model. Systematic calculations show that and has the
same attracting role as hyperon does in lighter hypernuclei.
and hyperon has the attracting role only for the protons
distribution, and has a repulsive role for the neutrons distribution. On the
contrary, and hyperon attracts surrounding neutrons and
reveals a repulsive force to the protons. We find that the different effect of
different baryons impurities on the nuclear core is due to the different third
component of their isospin.Comment: 9 page
First-principles investigation of 180-degree domain walls in BaTiO_3
We present a first-principles study of 180-degree ferroelectric domain walls
in tetragonal barium titanate. The theory is based on an effective Hamiltonian
that has previously been determined from first-principles
ultrasoft-pseudopotential calculations. Statistical properties are investigated
using Monte Carlo simulations. We compute the domain-wall energy, free energy,
and thickness, analyze the behavior of the ferroelectric order parameter in the
interior of the domain wall, and study its spatial fluctuations. An abrupt
reversal of the polarization is found, unlike the gradual rotation typical of
the ferromagnetic case.Comment: Revtex (preprint style, 13 pages) + 3 postscript figures. A version
in two-column article style with embedded figures is available at
http://electron.rutgers.edu/~dhv/preprints/index.html#pad_wal
The effect of additive noise on dynamical hysteresis
We investigate the properties of hysteresis cycles produced by a
one-dimensional, periodically forced Langevin equation. We show that depending
on amplitude and frequency of the forcing and on noise intensity, there are
three qualitatively different types of hysteresis cycles. Below a critical
noise intensity, the random area enclosed by hysteresis cycles is concentrated
near the deterministic area, which is different for small and large driving
amplitude. Above this threshold, the area of typical hysteresis cycles depends,
to leading order, only on the noise intensity. In all three regimes, we derive
mathematically rigorous estimates for expectation, variance, and the
probability of deviations of the hysteresis area from its typical value.Comment: 30 pages, 5 figure
Dynamic disorder in receptor-ligand forced dissociation experiments
Recently experiments showed that some biological noncovalent bonds increase
their lifetimes when they are stretched by an external force, and their
lifetimes will decrease when the force increases further. Several specific
quantitative models have been proposed to explain the intriguing transitions
from the "catch-bond" to the "slip-bond". Different from the previous efforts,
in this work we propose that the dynamic disorder of the force-dependent
dissociation rate can account for the counterintuitive behaviors of the bonds.
A Gaussian stochastic rate model is used to quantitatively describe the
transitions observed recently in the single bond P-selctin glycoprotein ligand
1(PSGL-1)P-selectin force rupture experiment [Marshall, {\it et al.}, (2003)
Nature {\bf 423}, 190-193]. Our model agrees well to the experimental data. We
conclude that the catch bonds could arise from the stronger positive
correlation between the height of the intrinsic energy barrier and the distance
from the bound state to the barrier; classical pathway scenario or {\it a
priori} catch bond assumption is not essential.Comment: 4 pages, 2 figure
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