Exact Results in Quantum Theory & Gravity

We prove a lower bound for the free energy of the two-dimensional dilute Bose gas in the thermodynamic limit. A matching upper bound has been obtained elsewhere. The resulting asymptotic formula for the free energy is interesting because the interaction term depends on the transition temperature of the Berezinskii–Kosterlitz–Thouless phase transition, which is conjectured to occur in the two-dimensional homogeneous Bose gas. This is joint work with Simon Maier and Robert Seiringer.