4,776 research outputs found
Slow Quenches Produce Fuzzy, Transient Vortices
We examine the Zurek scenario for the production of vortices in quenches of
liquid in the light of recent experiments. Extending our previous
results to later times, we argue that short wavelength thermal fluctuations
make vortices poorly defined until after the transition has occurred. Further,
if and when vortices appear, it is plausible that that they will decay faster
than anticipated from turbulence experiments, irrespective of quench rates.Comment: 4 pages, Revtex file, no figures Apart from a more appropriate title,
this paper differs from its predecessor by including temperature, as well as
pressure, quenche
Form factors in the Bullough-Dodd related models: The Ising model in a magnetic field
We consider particular modification of the free-field representation of the
form factors in the Bullough-Dodd model. The two-particles minimal form factors
are excluded from the construction. As a consequence, we obtain convenient
representation for the multi-particle form factors, establish recurrence
relations between them and study their properties. The proposed construction is
used to obtain the free-field representation of the lightest particles form
factors in the perturbed minimal models. As a significant example
we consider the Ising model in a magnetic field. We check that the results
obtained in the framework of the proposed free-field representation are in
agreement with the corresponding results obtained by solving the bootstrap
equations.Comment: 20 pages; v2: some misprints, textual inaccuracies and references
corrected; some references and remarks adde
Do attractive bosons condense?
Motivated by experiments on bose atoms in traps which have attractive
interactions (e.g. ^7Li), we consider two models which may be solved exactly.
We construct the ground states subject to the constraint that the system is
rotating with angular momentum proportional to the number of atoms. In a
conventional system this would lead to quantised vortices; here, for attractive
interactions, we find that the angular momentum is absorbed by the centre of
mass motion. Moreover, the state is uncondensed and is an example of a
`fragmented' condensate discussed by Nozi\`eres and Saint James. The same
models with repulsive interactions are fully condensed in the thermodynamic
limit.Comment: 4 pages, Latex, RevTe
Results of feasibility and safety of randomised controlled trial of a musculoskeletal exercise intervention versus usual care for children with haemophilia
Stationary solutions of the one-dimensional nonlinear Schroedinger equation: II. Case of attractive nonlinearity
All stationary solutions to the one-dimensional nonlinear Schroedinger
equation under box or periodic boundary conditions are presented in analytic
form for the case of attractive nonlinearity. A companion paper has treated the
repulsive case. Our solutions take the form of bounded, quantized, stationary
trains of bright solitons. Among them are two uniquely nonlinear classes of
nodeless solutions, whose properties and physical meaning are discussed in
detail. The full set of symmetry-breaking stationary states are described by
the character tables from the theory of point groups. We make
experimental predictions for the Bose-Einstein condensate and show that, though
these are the analog of some of the simplest problems in linear quantum
mechanics, nonlinearity introduces new and surprising phenomena.Comment: 11 pages, 9 figures -- revised versio
Fate of a Bose-Einstein condensate with attractive interaction
We calculate the decay amplitude of a harmonically trapped Bose-Einstein
condensate with attractive interaction via the Feynman path integral. We find
that when the number of particles is less than a critical number, the
condensate decays relatively slowly through quantum tunneling. When the number
exceeds the critical one, a "black hole" opens up at the center of the trap, in
which density fluctuations become large due to a negative pressure, and
collisional loss will drain the particles from the trap. As the black hole is
fed by tunneling particles, we have a novel system in which quantum tunneling
serves as a hydrodynamic source.Comment: 3 pages, REVTeX; email to [email protected] (Kerson Huang
Non-Ground-State Bose-Einstein Condensates of Trapped Atoms
The possibility of creating a Bose condensate of trapped atoms in a
non-ground state is suggested. Such a nonequilibrium Bose condensate can be
formed if one, first, obtains the conventional Bose condensate in the ground
state and then transfers the condensed atoms to a non-ground state by means of
a resonance pumping. The properties of ground and non-ground states are
compared and plausible applications of such nonequilibrium condensates are
discussed.Comment: 1 file, 16 pages, RevTe
Testing the Kibble-Zurek Scenario with Annular Josephson Tunnel Junctions
In parallel with Kibble's description of the onset of phase transitions in
the early universe, Zurek has provided a simple picture for the onset of phase
transitions in condensed matter systems, strongly supported by agreement with
experiments in He3. In this letter we show how experiments with annular
Josephson tunnel Junctions can and do provide further support for this
scenario.Comment: Revised version with correct formula for the Swihart velocity. The
results are qualitatively the same as with the previous version but differ
quantitatively. 4 pages, RevTe
Microscopic Treatment of Binary Interactions in the Non-Equilibrium Dynamics of Partially Bose-condensed Trapped Gases
In this paper we use microscopic arguments to derive a nonlinear
Schr\"{o}dinger equation for trapped Bose-condensed gases. This is made
possible by considering the equations of motion of various anomalous averages.
The resulting equation explicitly includes the effect of repeated binary
interactions (in particular ladders) between the atoms. Moreover, under the
conditions that dressing of the intermediate states of a collision can be
ignored, this equation is shown to reduce to the conventional Gross-Pitaevskii
equation in the pseudopotential limit. Extending the treatment, we show first
how the occupation of excited (bare particle) states affects the collisions,
and thus obtain the many-body T-matrix approximation in a trap. In addition, we
discuss how the bare particle many-body T-matrix gets dressed by mean fields
due to condensed and excited atoms. We conclude that the most commonly used
version of the Gross-Pitaevskii equation can only be put on a microscopic basis
for a restrictive range of conditions. For partial condensation, we need to
take account of interactions between condensed and excited atoms, which, in a
consistent formulation, should also be expressed in terms of the many-body
T-matrix. This can be achieved by considering fluctuations around the
condensate mean field beyond those included in the conventional finite
temperature mean field, i.e. Hartree-Fock-Bogoliubov (HFB), theory.Comment: Resolved some problems with printing of figure
Bose-Einstein condensation in a one-dimensional interacting system due to power-law trapping potentials
We examine the possibility of Bose-Einstein condensation in one-dimensional
interacting Bose gas subjected to confining potentials of the form , in which , by solving the
Gross-Pitaevskii equation within the semi-classical two-fluid model. The
condensate fraction, chemical potential, ground state energy, and specific heat
of the system are calculated for various values of interaction strengths. Our
results show that a significant fraction of the particles is in the lowest
energy state for finite number of particles at low temperature indicating a
phase transition for weakly interacting systems.Comment: LaTeX, 6 pages, 8 figures, uses grafik.sty (included), to be
published in Phys. Rev.
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