7 research outputs found
Mean-field expansion in Bose-Einstein condensates with finite-range interactions
We present a formal derivation of the mean-field expansion for dilute
Bose-Einstein condensates with two-particle interaction potentials which are
weak and finite-range, but otherwise arbitrary. The expansion allows for a
controlled investigation of the impact of microscopic interaction details
(e.g., the scaling behavior) on the mean-field approach and the induced
higher-order corrections beyond the s-wave scattering approximation.Comment: 6 pages of RevTex4; extended discussion, added reference
Quantum backreaction in dilute Bose-Einstein condensates
For many physical systems which can be approximated by a classical background
field plus small (linearized) quantum fluctuations, a fundamental question
concerns the correct description of the backreaction of the quantum
fluctuations onto the dynamics of the classical background. We investigate this
problem for the example of dilute atomic/molecular Bose-Einstein condensates,
for which the microscopic dynamical behavior is under control. It turns out
that the effective-action technique does not yield the correct result in
general and that the knowledge of the pseudo-energy-momentum tensor is not sufficient to describe quantum backreaction.Comment: 8 pages of RevTex4; extended discussion with additional sections, to
be published in Physical Review
Dispersive fields in de Sitter space and event horizon thermodynamics
When Lorentz invariance is violated at high energy, the laws of black hole
thermodynamics are apparently no longer satisfied. To shed light on this
observation, we study dispersive fields in de Sitter space. We show that the
Bunch-Davies vacuum state restricted to the static patch is no longer thermal,
and that the Tolman law is violated. However we also show that, for free fields
at least, this vacuum is the only stationary stable state, as if it were in
equilibrium. We then present a precise correspondence between dispersive
effects found in de Sitter and in black hole metrics. This indicates that the
consequences of dispersion on thermodynamical laws could also be similar.Comment: 19 pages. Black and White version on Phys.Rev.D serve
Cavitation induced by explosion in a model of ideal fluid
We discuss the problem of an explosion in the cubic-quintic superfluid model,
in relation to some experimental observations. We show numerically that an
explosion in such a model might induce a cavitation bubble for large enough
energy. This gives a consistent view for rebound bubbles in superfluid and we
indentify the loss of energy between the successive rebounds as radiated waves.
We compute self-similar solution of the explosion for the early stage, when no
bubbles have been nucleated. The solution also gives the wave number of the
excitations emitted through the shock wave.Comment: 21 pages,13 figures, other comment
Coexisting ordinary elasticity and superfluidity in a model of defect-free supersolid
We present the mechanics of a model of supersolid in the frame of the
Gross-Pitaevskii equation at that do not require defects nor vacancies.
A set of coupled nonlinear partial differential equations plus boundary
conditions is derived. The mechanical equilibrium is studied under external
constrains as steady rotation or external stress. Our model displays a
paradoxical behavior: the existence of a non classical rotational inertia
fraction in the limit of small rotation speed and no superflow under small (but
finite) stress nor external force. The only matter flow for finite stress is
due to plasticity.Comment: 6 pages, 2 figure
Quasiparticle universes in Bose-Einstein condensates
Recent developments in simulating fundamental quantum field theoretical
effects in the kinematical context of analogue gravity are reviewed.
Specifically, it is argued that a curved space-time generalization of the
Unruh-Davies effect -- the Gibbons-Hawking effect in the de Sitter space-time
of inflationary cosmological models -- can be implemented and verified in an
ultracold gas of bosonic atoms.Comment: 23 pages, 2 figures; invited brief review for Modern Physics Letters
A, as publishe