Atom interferometric detection of the pairing order parameter in a Fermi gas

We propose two interferometric schemes to experimentally detect the onset of pair condensation in a two spin-component Fermi gas. Two atomic wave-packets are coherently extracted from the gas at different positions and are mixed by a matter-wave beam splitter: we show that the spatial long range order of the atomic pairs in the gas then reflects in the atom counting statistics in the output channels of the beam splitter. Alternatively, the same long range order is also shown to create a matter-wave grating in the overlapping region of the two extracted wave-packets, grating that can be revealed by a light scattering experiment

One particle in a box: the simplest model for a Fermigas in the unitary limit

We consider a single quantum particle in a spherical box interacting with a fixed scatterer at the center, to construct a model of a degenerate atomic Fermi gas close to a Feshbach resonance. One of the key predictions of the model is the existence of two branches for the macroscopic state of the gas, as a function of the magnetic field controlling the value of the scattering length.This model is able to draw a qualitative picture of all the different features recently observed in a degenerate atomic Fermi gas close to the resonance, even in the unitary limit

Energy transfer mechanisms in adverse pressure gradient turbulent boundary layers

The energy transfer mechanisms and structures playing a role in these mechanisms in adverse-pressure-gradient (APG) turbulent boundary layers (TBLs) with small and large velocity defects are investigated. We examine the wall-normal and spectral distributions of energy, production and pressure-strain in APG TBLs and compare these distributions with those in canonical flows. It is found that the spectral distributions of production and pressure-strain are not profoundly affected by an increase of the velocity defect, although the energy spectra drastically change in the inner layer of the large defect APG TBL. In the latter, the signature of the inner layer streaks is absent from the energy spectra. However, the production and pressure-strain spectra suggest that the near-wall cycle or another energy transfer mechanism with similar spectral features still exist in large defect TBLs. In the outer layer, energetic, production and pressure-strain structures appear to change from wall-attached to wall-detached structures with increasing velocity defect. Despite this, the 2D spectral distributions have similar shapes and wavelength aspect ratios of the peaks in all these flows. These observations suggest that outer layer energy transfer mechanisms may be the same in wall-bounded flows, no matter if dynamically relevant structures are attached or detached to the wall. Therefore, the conclusion is that the mechanisms responsible for turbulence production and inter-component energy transfer may remain the same within each layer in all these flows. It is the intensity of these mechanisms within one layer that changes with velocity defect, because of the local mean shear variation

Boundary states for a free boson defined on finite geometries

Langlands recently constructed a map that factorizes the partition function of a free boson on a cylinder with boundary condition given by two arbitrary functions in the form of a scalar product of boundary states. We rewrite these boundary states in a compact form, getting rid of technical assumptions necessary in his construction. This simpler form allows us to show explicitly that the map between boundary conditions and states commutes with conformal transformations preserving the boundary and the reality condition on the scalar field.Comment: 16 pages, LaTeX (uses AMS components). Revised version; an analogy with string theory computations is discussed and references adde

Pluralité culturelle à l'école: les apports de la psychologie interculturelle

La psychologie interculturelle examine les processus psychologiques dans leur contexte culturel. Elle permet de prendre du recul par rapport à une psychologie ethnocentrique, élaborée uniquement dans un contexte occidental. Le potentiel d'application dans le milieu scolaire mérite d'être développé de façon plus explicite, en prenant en compte d'une part le développement cognitif, d'autre part les relations intergroupes et la communication interculturelle, enfin les psychologies sociales, scolaires et clinique