1,855 research outputs found
Thomas-Fermi Approximation for a Condensate with Higher-order Interactions
We consider the ground state of a harmonically trapped Bose-Einstein
condensate within the Gross-Pitaevskii theory including the effective-range
corrections for a two-body zero-range potential. The resulting non-linear
Schr\"odinger equation is solved analytically in the Thomas-Fermi approximation
neglecting the kinetic energy term. We present results for the chemical
potential and the condensate profiles, discuss boundary conditions, and compare
to the usual Thomas-Fermi approach. We discuss several ways to increase the
influence of effective-range corrections in experiment with magnetically
tunable interactions. The level of tuning required could be inside experimental
reach in the near future.Comment: 8 pages, RevTex4 format, 5 figure
On the size of the smallest scales in cosmic string networks
We present a method for the calculation of the gravitational back reaction
cutoff on the smallest scales of cosmic string networks taking into account
that not all modes on strings interact with all other modes. This results in a
small scale structure cutoff that is sensitive to the initial spectrum of
perturbations present on strings. From a simple model, we compute the cutoffs
in radiation- and matter-dominated universes.Comment: 4 pages, revte
Cosmic String Cusps with Small-Scale Structure: Their Forms and Gravitational Waveforms
We present a method for the introduction of small-scale structure into
strings constructed from products of rotation matrices. We use this method to
illustrate a range of possibilities for the shape of cusps that depends on the
properties of the small-scale structure. We further argue that the presence of
structure at cusps under most circumstances leads to the formation of loops at
the size of the smallest scales. On the other hand we show that the
gravitational waveform of a cusp remains generally unchanged; the primary
effect of small-scale structure is to smooth out the sharp waveform emitted in
the direction of cusp motion.Comment: RevTeX, 8 pages. Replaced with version accepted for publication by
PR
Flow and equation of state in heavy-ion collisions
The status of flow in heavy-ion collisions and of inference of
hadronic-matter properties is reviewed.Comment: 11 pages, 12 figures, talk given at Quark Matter '99, Torino, Ital
Stability of bubble nuclei through Shell-Effects
We investigate the shell structure of bubble nuclei in simple
phenomenological shell models and study their binding energy as a function of
the radii and of the number of neutron and protons using Strutinsky's method.
Shell effects come about, on the one hand, by the high degeneracy of levels
with large angular momentum and, on the other, by the big energy gaps between
states with a different number of radial nodes. Shell energies down to -40 MeV
are shown to occur for certain magic nuclei. Estimates demonstrate that the
calculated shell effects for certain magic numbers of constituents are probably
large enough to produce stability against fission, alpha-, and beta-decay. No
bubble solutions are found for mass number A < 450.Comment: 9 pages and 9 figures in the eps format include
Chi-square test on candidate events from CW signal coherent searches
In a blind search for continuous gravitational wave signals scanning a wide
frequency band one looks for candidate events with significantly large values
of the detection statistic. Unfortunately, a noise line in the data may also
produce a moderately large detection statistic.
In this paper, we describe how we can distinguish between noise line events
and actual continuous wave (CW) signals, based on the shape of the detection
statistic as a function of the signal's frequency. We will analyze the case of
a particular detection statistic, the F statistic, proposed by Jaranowski,
Krolak, and Schutz.
We will show that for a broad-band 10 hour search, with a false dismissal
rate smaller than 1e-6, our method rejects about 70 % of the large candidate
events found in a typical data set from the second science run of the Hanford
LIGO interferometer.Comment: proceedings of GWDAW8, 2003 conference, 12pages, 6 figure
Neutrino-Nucleus Reactions and Muon Capture in 12C
The neutrino-nucleus cross section and the muon capture rate are discussed
within a simple formalism which facilitates the nuclear structure calculations.
The corresponding formulae only depend on four types of nuclear matrix
elements, which are currently used in the nuclear beta decay. We have also
considered the non-locality effects arising from the velocity-dependent terms
in the hadronic current. We show that for both observables in 12C the higher
order relativistic corrections are of the order of ~5 only, and therefore do
not play a significant role. As nuclear model framework we use the projected
QRPA (PQRPA) and show that the number projection plays a crucial role in
removing the degeneracy between the proton-neutron two quasiparticle states at
the level of the mean field. Comparison is done with both the experimental data
and the previous shell model calculations. Possible consequences of the present
study on the determination of the neutrino oscillation
probability are briefly addressed.Comment: 29 pages, 6 figures, Revtex4. Several changes were made to the
previous manuscript, the results and final conclusions remain unalterable. It
has been accepted for publication as a Regular Article in Physical Review
The Transverse Structure of the Baryon Source in Relativistic Heavy Ion Collisions
A direct method to reconstruct the transverse structure of the baryon source
formed in a relativistic heavy ion collision is presented. The procedure makes
use of experimentally measured proton and deuteron spectra and assumes that
deuterons are formed via two-nucleon coalescence. The transverse density shape
and flow profile are reconstructed for Pb+Pb collisions at the CERN-SPS. The
ambiguity with respect to the source temperature is demonstrated and possible
ways to resolve it are discussed.Comment: 15 pages LaTeX, 4 postscript figures, uses psfig.sty - Revised
version, few minor change
Cosmological stretching of perturbations on a cosmic string
We investigate the effects of cosmological expansion on the spectrum of
small-scale structure on a cosmic string. We simulate the evolution of a string
with two modes that differ in wavelength by one order of magnitude. Once the
short mode is inside the horizon, we find that its physical amplitude remains
unchanged, in spite of the fact that its comoving wavelength decreases as the
longer mode enters the horizon. Thus the ratio of amplitude to wavelength for
the short mode becomes larger than it would be in the absence of the long mode.Comment: 11 pages, 5 postscript figure
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