## Seminar on Theoretical Nuclear Physics

## 25.01.11 16:15

# Efimovian states in the few-body problem

## Christophe Mora (Paris)

The possibility to control interactions using Feshbach resonances in cold atoms has opened numerous directions of research in the recent years. One of them is the study of few-body systems in a resonant regime where zero range models apply and lead to universal predictions. We discuss the Efimov effect for three identical bosons, corresponding to the emergence of an infinite hierarchy of bound states (Efimov trimers) with an accumulation point in the spectrum at zero energy. Using a narrow Feshbach resonance as a toy model, we can give an analytical solution to the three-body problem by mapping it to an effective one-dimensional Schroedinger equation. We also consider the case of three fermions with a lighter particle for which a four-body Efimovian state appears in a particular interval of mass ratio.

(Seminarraum II)