We show that, under very general definitions of a kinetic energy operator
$T$, the Lieb-Thirring inequalities for sums of eigenvalues of $T-V$ can be
derived from the Sobolev inequality appropriate to that choice of $T$.
Since the first experimental realization of Bose-Einstein condensation in
cold atomic gases in 1995 there has been a surge of activity in this field.
Ingenious experiments have allowed us to probe matter close to zero temperature
and reveal some of the fascinating effects quantum mechanics has bestowed on
nature. It is a challenge for mathematical physicists to understand these
various phenomena from first principles, that is, starting from the underlying
many-body Schr\"odinger equation.