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Atomes ultra-froids

In spite of the important differences in typical energy and size scales, many analogies exist between nuclei and ultra-cold gases of trapped atoms.

In the last decade, experiments studying dilute gases of electrically neutral atoms in artificial optical or magneto-optical potentials made tremendous progress. In the case of fermionic atoms in a trap, the close analogy between these systems and nuclei where nucleons move in the mean field is evident. Many concepts of nuclear physics, such as pairing and collective modes, have also been studied in cold atoms, and a fruitful exchange between the two fields has developed. Recently, we were mainly interested in the transition from the hydrodynamic to the collisionless regime, as the temperature of the gas increases, the gas expands, and the collision rate of the atoms decreases. Good agreement with the experimentally measured frequencies and damping rates of quadrupole and dipole modes was obtained.

Another subject studied by the group is atoms with magnetic dipole-dipole interactions. This topic is very timely since the first degenerate dipolar Fermi gas was created only very recently. The dipole-dipole interaction is also interesting from the nuclear physics point of view, since it is very similar to the tensor force between nucleons. We have shown that in the case of dipolar atoms, a new instability of the Hartree-Fock ground state with a spherical Fermi surface can appear, which leads to the formation of a spin texture in momentum space.



Institut de Physique Nucléaire Orsay - 15 rue Georges CLEMENCEAU - 91406 ORSAY (FRANCE)
UMR 8608 - CNRS/IN2P3

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