@unpublished{7524,
  abstract     = {We prove a lower bound for the free energy (per unit volume) of the two-dimensional Bose gas in the thermodynamic limit. We show that the free energy at density $\rho$ and inverse temperature $\beta$ differs from the one of the non-interacting system by the correction term $4 \pi \rho^2 |\ln a^2 \rho|^{-1} (2 - [1 - \beta_{\mathrm{c}}/\beta]_+^2)$. Here $a$ is the scattering length of the interaction potential, $[\cdot]_+ = \max\{ 0, \cdot \}$ and $\beta_{\mathrm{c}}$ is the inverse Berezinskii--Kosterlitz--Thouless critical temperature for superfluidity. The result is valid in the dilute limit
$a^2\rho \ll 1$ and if $\beta \rho \gtrsim 1$.},
  author       = {Deuchert, Andreas and Mayer, Simon and Seiringer, Robert},
  booktitle    = {arXiv},
  pages        = {61},
  title        = {{The free energy of the two-dimensional dilute Bose gas. I. Lower bound}},
  doi          = {10.48550/arXiv.1910.03372},
  year         = {2019},
}