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We simulate numerically the free expansion of a repulsive Bose-Einstein condensate with an initially Gaussian density profile. We find a self-similar expansion only for weak inter-atomic repulsion. In contrast, for strong repulsion we observe the spontaneous formation of a shock wave at the surface followed by a significant depletion inside the cloud. In the expansion, contrary to the case of a classical viscous gas, the quantum fluid can generate radial rarefaction density waves with several minima and maxima. These intriguing nonlinear effects, never observed yet in free-expansion experiments with ultra-cold alkali-metal atoms, can be detected with the available setups.
We propose and analyze a general mechanism of disorder-induced order in two-component Bose-Einstein condensates, analogous to corresponding effects established for XY spin models. We show that a random Raman coupling induces a relative phase of pi/2
We develop a pairing mean-field theory to describe the quantum dynamics of the dissociation of molecular Bose-Einstein condensates into their constituent bosonic or fermionic atoms. We apply the theory to one, two, and three-dimensional geometries an
We investigate dynamical properties of bright solitons with a finite background in the F=1 spinor Bose-Einstein condensate (BEC), based on an integrable spinor model which is equivalent to the matrix nonlinear Schr{o}dinger equation with a self-focus
Phase transitions are ubiquitous in nature, ranging from protein folding and denaturisation, to the superconductor-insulator quantum phase transition, to the decoupling of forces in the early universe. Remarkably, phase transitions can be arranged in
We have theoretically studied vortex waves of Bose-Einstein condensates in elongated harmonic traps. Our focus is on the axisymmetric varicose waves and helical Kelvin waves of singly quantized vortex lines. Growth and decay dynamics of both types of