We apply the microscopic Bogoliubov theory of dilute Bose-Einstein condensates to analyze quantum and thermal fluctuations in a flowing atomic condensate presence sonic horizon. For simplest case step-like horizon, closed-form analytical expressions are found for spectral distribution analog Hawking radiation density correlation function. The peculiar long-distance correlations that appear as consequence emission features turns out be reinforced by finite initial temperature condensate....

We compute the stationary profiles of a coherent beam Bose condensed atoms propagating through guide. Special emphasis is put on effect an obstacle present trajectory beam. The considered (such as bend in guide, or laser field perpendicular to beam) results repulsive attractive potential acting condensate. Different behaviors are observed when varying velocity (with respect speed sound), size (relative healing length) and intensity sign potential. existence bound states condensate also considered.

We study several realistic configurations making it possible to realize an acoustic horizon in the flow of a one-dimensional Bose-Einstein condensate. In each case we give analytical description pattern, spectrum Hawking radiation, and associated quantum fluctuations. Our calculations confirm that nonlocal correlations density fluctuations previously studied simplified model provide clear signature radiation also configurations. addition, explain by direct computation how this signal relates...

We study the quantum fluctuations in a one-dimensional Bose-Einstein condensate realizing an analogous acoustic black hole. The taking into account of evanescent channels and zero modes makes it possible to accurately reproduce recent experimental measurements density correlation function. discuss determination Hawking temperature show that our model radiation presents some significant departure from thermality.

The one-dimensional flow of a continuous beam Bose-Einstein condensed atoms in the presence an obstacle is studied as function velocity and type perturbing potential (representing interaction with beam). We identify relevant regimes: stationary/time-dependent superfluid/dissipative; absence drag used criterion for superfluidity. There exists critical below which superfluid. For attractive obstacles, we show that this can reach value predicted by Landau's approach. Besides, penetrable it...

We consider the motion of a quasi-one-dimensional beam Bose-Einstein condensed particles in disordered region finite extent. Interaction effects lead to appearance two distinct regions stationary flow. One is subsonic and corresponds superfluid motion. The other one supersonic dissipative shows Anderson localization. compute analytically interaction-dependent localization length. also explain disappearance flow for large samples.

We consider a sonic analog of black hole realized in the one-dimensional flow Bose-Einstein condensate. Our theoretical analysis demonstrates that one- and two-body momentum distributions accessible by present-day experimental techniques provide clear direct evidence (i) occurrence horizon, (ii) associated acoustic Hawking radiation, (iii) quantum nature process. The signature behavior persists even at temperatures larger than chemical potential.Received 2 March...

We study the dynamics of a spin- \frac{1}{2} <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mfrac><mml:mn>1</mml:mn><mml:mn>2</mml:mn></mml:mfrac></mml:math> XXZ chain which is initially prepared in domain-wall state. compare results time-dependent Density Matrix Renormalization Group simulations with those an effective description terms classical anisotropic Landau-Lifshitz (LL) equation. Numerous quantities are analyzed: magnetization ( x...

We report on the formation of a dispersive shock wave in nonlinear optical medium. monitor evolution by tuning incoming beam power. The experimental observations for position and intensity solitonic edge shock, as well location oscillations are described recent developments Whitham modulation theory. Our work constitutes detailed accurate benchmark this approach. It opens exciting possibilities to engineer specific configurations studying wave-mean flow interaction.

We present experimental and theoretical results on formation of quantum vortices in a laser beam propagating nonlinear medium. Topological constrains richer than the mere conservation vorticity impose an elaborate dynamical behavior to annihilation vortex-antivortex pairs. identify two such mechanisms, both described by same fold-Hopf bifurcation. One them is particularly efficient although it not observed context liquid helium films or stationary systems because relies compressible nature...

Motivated by recent experiments on generation of wave patterns a polariton condensate incident localized obstacle, we study the characteristics such flows under condition that irreversible processes play crucial role in system. The dynamics non-resonantly pumped quasi-one-dimensional quantum wire is modeled Gross-Pitaevskii equation with additional phenomenological terms accounting for dissipation and pumping processes. response flow to an external potential describing obstacle considered...

We study the coherent flow of a guided Bose-Einstein condensate incident over disordered region length L. introduce model potential that originates from magnetic fluctuations inherent to microfabricated guides. This allows for analytical and numerical studies realistic transport experiments. The repulsive interaction among atoms in beam induces different regimes. Below some critical (or sufficiently small L) stationary is observed. In this regime, transmission decreases exponentially with...

We study the flow of a quasi-one-dimensional Bose-Einstein condensate incident onto narrow obstacle. consider configuration in which dispersive shock is formed and propagates upstream away from obstacle while downstream reaches supersonic velocity, generating sonic horizon. Conditions for obtaining this regime are explicitly derived accuracy our analytical results confirmed by numerical simulations.

We provide a classification of the possible flows two-component Bose-Einstein condensates evolving from initially discontinuous profiles. consider situation where dynamics can be reduced to consideration single polarization mode (also denoted as ``magnetic excitation'') obeying system equations equivalent Landau-Lifshitz equation for an easy-plane ferromagnet. present full set one-phase periodic solutions. The corresponding Whitham modulation are obtained together with formulas connecting...

A two-component Bose-Einstein condensate whose dynamics is described by a system of coupled Gross-Pitaevskii equations accommodates waves with different symmetries. first type corresponds to excitations for which the motion both components locally in phase. For second waves, two have counterphase local motion. When values inter- and intracomponent interaction constants are different, long-wavelength behavior these modes types sound velocities. In limit weak nonlinearity small dispersion,...

We consider the space-time evolution of initial discontinuities depth and flow velocity for an integrable version shallow water Boussinesq system introduced by Kaup. focus on a specific this “Kaup-Boussinesq model” which flat surface is modulationally stable, we speak below “positive dispersion” model. This model also appears as approximation to equations governing dynamics polarisation waves in two-component Bose-Einstein condensates. describe its periodic solutions corresponding Whitham...

We consider dipole oscillations of a trapped dilute Bose-Einstein condensate in the presence scattering potential consisting either localized defect or an extended disordered potential. In both cases breaking superfluidity and damping are shown to be related appearance nonlinear dissipative flow. At supersonic velocities flow becomes asymptotically dissipationless.

We consider the phase coherent transport of a quasi-one-dimensional beam Bose-Einstein condensed particles through disordered potential length $L$. Among possible different types flow we identified [T. Paul, P. Schlagheck, Leboeuf, and N. Pavloff, Phys. Rev. Lett. 98, 210602 (2007)], focus here on supersonic stationary regime where Anderson localization exists. generalize diffusion formalism Dorokhov-Mello-Pereyra-Kumar to include interaction effects. It is shown that interactions modify...