340 research outputs found
Trace formula for an ensemble of bumpy billiards.
We study the semiclassical quantization of an ensemble of billiards with a
small random shape deformation. We derive a trace formula averaged over shape
disorder. The results are illustrated by the study of supershells in rough
metal clusters.Comment: 12 pages, latex, 3 figures available by fax upon request
Hawking radiation in a two-component Bose-Einstein condensate
We consider a simple realization of an event horizon in the flow of a
one-dimensional two-component Bose-Einstein condensate. Such a condensate has
two types of quasiparticles; In the system we study, one corresponds to density
fluctuations and the other to polarization fluctuations. We treat the case
where a horizon occurs only for one type of quasiparticles (the polarization
ones). We study the one- and two-body signal associated to the analog of
spontaneous Hawking radiation and demonstrate by explicit computation that it
consists only in the emission of polarization waves. We discuss the
experimental consequences of the present results in the domain of atomic
Bose-Einstein condensates and also for the physics of exciton-polaritons in
semiconductor microcavities
Interference effects in the two-dimensional scattering of microcavity polaritons by an obstacle: phase dislocations and resonances
We consider interference effects within the linear description of the
scattering of two-dimensional microcavity polaritons by an obstacle. The
polariton wave may exhibit phase dislocations created by the interference of
the incident and the scattered fields. We describe these structures within the
general framework of singular optics. We also discuss another type of
interference effects appearing due to the formation of (quasi)resonances in the
potential of a repulsive obstacle with sharp boundaries. We discuss the
relevance of our approach for the description of recent experimental results
and propose a criterion for evaluating the importance of nonlinear effects.Comment: 11 pages, 9 figure
Dispersive hydrodynamics of nonlinear polarization waves in two-component Bose-Einstein condensates
We study one dimensional mixtures of two-component Bose-Einstein condensates in the limit where the intra-species and inter-species interaction constants are very close. Near the mixing-demixing transition the polarization and the density dynamics decouple. We study the nonlinear polarization waves, show that they obey a universal (i.e., parameter free) dynamical description, identify a new type of algebraic soliton, explicitly write simple wave solutions, and study the Gurevich-Pitaevskii problem in this context
Nonlinear waves in coherently coupled Bose-Einstein condensates
We consider a quasi-one-dimensional two-component Bose-Einstein condensate
subject to a coherent coupling between its components, such as realized in
spin-orbit coupled condensates. We study how nonlinearity modifies the dynamics
of the elementary excitations. The spectrum has two branches which are affected
in different ways. The upper branch experiences a modulational instability
which is stabilized by a long wave-short wave resonance with the lower branch.
The lower branch is stable. In the limit of weak nonlinearity and small
dispersion it is described by a Korteweg-de Vries equation or by the Gardner
equation, depending on the value of the parameters of the system
Bogoliubov Theory of acoustic Hawking radiation in Bose-Einstein Condensates
We apply the microscopic Bogoliubov theory of dilute Bose-Einstein
condensates to analyze quantum and thermal fluctuations in a flowing atomic
condensate in the presence of a sonic horizon. For the simplest case of a
step-like horizon, closed-form analytical expressions are found for the
spectral distribution of the analog Hawking radiation and for the density
correlation function. The peculiar long-distance density correlations that
appear as a consequence of the Hawking emission features turns out to be
reinforced by a finite initial temperature of the condensate. The analytical
results are in good quantitative agreement with first principle numerical
calculations.Comment: 11 pages, 7 figure
Propagation of a Dark Soliton in a Disordered Bose-Einstein Condensate
We consider the propagation of a dark soliton in a quasi 1D Bose-Einstein
condensate in presence of a random potential. This configuration involves
nonlinear effects and disorder, and we argue that, contrarily to the study of
stationary transmission coefficients through a nonlinear disordered slab, it is
a well defined problem. It is found that a dark soliton decays algebraically,
over a characteristic length which is independent of its initial velocity, and
much larger than both the healing length and the 1D scattering length of the
system. We also determine the characteristic decay time.Comment: 4 pages, 2 figure
Polarization hydrodynamics in a one-dimensional polariton condensate
We study the hydrodynamics of a nonresonantly-pumped polariton condensate in
a quasi-one-dimensional quantum wire taking into account the spin degree of
freedom. We clarify the relevance of the Landau criterion for superfluidity in
this dissipative two-component system. Two Cherenkov-like critical velocities
are identified corresponding to the opening of different channels of radiation:
one of (damped) density fluctuations and another of (weakly damped)
polarization fluctuations. We determine the drag force exerted onto an external
obstacle and propose experimentally measurable consequences of the specific
features of the fluctuations of polarization
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