We study the relaxation dynamics of an isolated zero temperature quasi-two-dimensional superfluid Bose-Einstein condensate that is imprinted with a spatially random distribution of quantum vortices. Following a period of vortex annihilation the remaining vortices self-organize into two macroscopic coherent "Onsager vortex" clusters that are stable indefinitely--despite the absence of driving or...

A technology program was started in 1994 within the framework of the German Aeronautics Research Program to develop axial staged combustor technology up to a core engine demonstrator. The objective was to demonstrate a 50% NOx reduction against the ICAO CAEP II limit without any compromise on the CO, UHC and smoke emission level compared to the latest single annular combustor technology. All ot...

The objectives of this work are (i) to investigate the coupled unsteady heat release mechanisms responsible for thermoacoustic instabilities under di erent ame anchoring con gurations, (ii) to develop reduced-order models to predict the dynamic ame response, and (iii) to develop passive instability mitigation strategies by modifying the dynamics of the ame anchoring zone. The two di erent ancho...

We describe different types of self-trapped optical beams carrying phase dislocations, including vortex solitons and ring-like soliton clusters. We demonstrate numerically how to create such nonlinear singular beams by the interaction of several fundamental optical solitons. Mutual trapping of several solitons can be regarded as a synthesis of ‘soliton molecules’, and it corresponds to a transf...

We study spatially localized optical vortices created by self-trapping of partially incoherent light with a phase dislocation in a biased photorefractive crystal. In contrast to a decay of coherent self-trapped vortex beams due to the azimuthal modulational instability, the incoherent vortices are stabilized for large values of the spatial incoherence; this was confirmed by experiment. We analy...

In a numerical experiment based on Gross-Pitaevskii formalism, we demonstrate unique topological quantum coherence in optically trapped Bose-Einstein condensates (BECs). Exploring the fact that vortices in rotating BEC can be pinned by a geometric arrangement of laser beams, we show the parameter range in which vortex-antivortex molecules or multiquantum vortices are formed as a consequence of ...

We numerically integrate the one-dimensional, cylindrically symmetric Ginzburg-Landau equations to calculate the spatial variation of the order parameter and supercurrents for a vortex trapped by a cylindrical defect. We use the resulting field distributions to estimate the pinning energy, and make use of the vortex/twodimensional boson analogy to calculate the depinning temperature. The micros...

In a benchmark dynamical-lattice model in three dimensions, the discrete nonlinear Schrödinger equation, we find discrete vortex solitons with various values of the topological charge S. Stability regions for the vortices with S=0,1,3 are investigated. The S=2 vortex is unstable and may spontaneously rearranging into a stable one with S=3. In a two-component extension of the model, we find a no...

(Dated: April 14, 2008) We study the dynamics of vortex lattice formation of a rotating trapped Bose-Einstein condensate by numerically solving the two-dimensional Gross-Pitaevskii equation, and find that the condensate undergoes elliptic deformation, followed by unstable surface-mode excitations before forming a quantized vortex lattice. The origin of the peculiar surface-mode excitations is i...