Long-range forces in quantum gases : the three-body problem and the Efimov effect

Since Newton's work, the three-body problem has fascinated generations of physicists and mathematicians. In quantum physics, a remarkable effect, predicted in 1970 by Vitaly Efimov, appears at low energies : when the supposedly short-range two-body interaction becomes resonant, a long-range interaction potential emerges for the three-body system body ; this system then becomes scale-invariant, and the position of its energy levels obeys a simple, universal mathematical law. This law has been verified thanks to recent advances in quantum gas physics. The lecture will be devoted to the theoretical description of this Efimov effect and to the presentation of some of its experimental manifestations.