Strongly correlated systems in few-body land

This colloquium will discuss some of the nonperturbative
physics that occurs when a few particles interact strongly, stressing
low-energy phenomena where one needs to go beyond perturbation theory.
Some of the problems of recent interest include the recombination of 3
or 4 or even 5 ultracold atoms to form molecules, a key process that
tends to eject atoms and cause losses from a Bose-Einstein condensate.
Resonances in this system are connected with the intriguing Efimov
effect.  Another recent interest has been the field of artificial gauge
potentials in cold atom physics, where an appropriate laser dressing of
neutral atoms causes them to behave as though they were charged
particles in a magnetic field or even with artificial spin-orbit
coupling.  I will discuss recent developments that allow the theory to
treat such systems quantitatively and also enable qualitative intuition
to be developed, in the context of recent experiments.