Nonlinear coherent transport of waves in disordered media

We present a diagrammatic theory for coherent backscattering from disordered dilute media in the nonlinear regime. The approach is non-perturbative in the strength of the nonlinearity. We show that the coherent backscattering enhancement factor is strongly affected by the nonlinearity, and corroborate these results by numerical simulations. Our theory can be applied to several physical scenarios like scattering of light in nonlinear Kerr media, or propagation of matter waves in disordered potentials.Comment: 4 pages, 3 figure

Coherent Backscattering of Light with Nonlinear Atomic Scatterers

We study coherent backscattering of a monochromatic laser by a dilute gas of cold two-level atoms in the weakly nonlinear regime. The nonlinear response of the atoms results in a modification of both the average field propagation (nonlinear refractive index) and the scattering events. Using a perturbative approach, the nonlinear effects arise from inelastic two-photon scattering processes. We present a detailed diagrammatic derivation of the elastic and inelastic components of the backscattering signal both for scalar and vectorial photons. Especially, we show that the coherent backscattering phenomenon originates in some cases from the interference between three different scattering amplitudes. This is in marked contrast with the linear regime where it is due to the interference between two different scattering amplitudes. In particular we show that, if elastically scattered photons are filtered out from the photo-detection signal, the nonlinear backscattering enhancement factor exceeds the linear barrier two, consistently with a three-amplitude interference effect.Comment: 18 pages, 13 figures, submitted to Phys. Rev.

Diagrammatic approach to coherent backscattering of laser light by cold atoms: Double scattering revisited

We present a diagrammatic derivation of the coherent backscattering spectrum from two two-level atoms using the pump-probe approach, wherein the multiple scattering signal is deduced from single-atom responses, and provide a physical interpretation of the single-atom building blocks.Comment: 16 pages, 7 figure

Number-conserving master equation theory for a dilute Bose-Einstein condensate

We describe the transition of $N$ weakly interacting atoms into a Bose-Einstein condensate within a number-conserving quantum master equation theory. Based on the separation of time scales for condensate formation and non-condensate thermalization, we derive a master equation for the condensate subsystem in the presence of the non-condensate environment under the inclusion of all two body interaction processes. We numerically monitor the condensate particle number distribution during condensate formation, and derive a condition under which the unique equilibrium steady state of a dilute, weakly interacting Bose-Einstein condensate is given by a Gibbs-Boltzmann thermal state of $N$ non-interacting atoms

A new species of <i>Ocyale</i> (Araneae, Lycosidae) from Madagascar, with first observations on the biology of a representative in the genus

A large white species of wolf spider, Ocyale ghost Jocque M. & Jocque R. sp. nov., is described from a white sandy beach of an inland freshwater lake in the northwest of Madagascar. The first photos of a living specimen of the genus Ocyale are provided together with some observations on the biology of the newly described species. An updated and illustrated key to the Afrotropical species of Ocyale is included here