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THE FREE ENERGY OF THE TWO-DIMENSIONAL DILUTE BOSE GAS. I. LOWER BOUND

Published online by Cambridge University Press:  21 April 2020

ANDREAS DEUCHERT
Affiliation:
Institute of Mathematics, University of Zurich, Winterthurerstrasse 190, 8057Zurich, Switzerland; andreas.deuchert@math.uzh.ch Institute of Science and Technology Austria (IST Austria), Am Campus 1, 3400Klosterneuburg, Austria; simon.mayer@ist.ac.at, robert.seiringer@ist.ac.at
SIMON MAYER
Affiliation:
Institute of Science and Technology Austria (IST Austria), Am Campus 1, 3400Klosterneuburg, Austria; simon.mayer@ist.ac.at, robert.seiringer@ist.ac.at
ROBERT SEIRINGER
Affiliation:
Institute of Science and Technology Austria (IST Austria), Am Campus 1, 3400Klosterneuburg, Austria; simon.mayer@ist.ac.at, robert.seiringer@ist.ac.at

Abstract

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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 $\unicode[STIX]{x1D70C}$ and inverse temperature $\unicode[STIX]{x1D6FD}$ differs from the one of the noninteracting system by the correction term $4\unicode[STIX]{x1D70B}\unicode[STIX]{x1D70C}^{2}|\ln \,a^{2}\unicode[STIX]{x1D70C}|^{-1}(2-[1-\unicode[STIX]{x1D6FD}_{\text{c}}/\unicode[STIX]{x1D6FD}]_{+}^{2})$. Here, $a$ is the scattering length of the interaction potential, $[\cdot ]_{+}=\max \{0,\cdot \}$ and $\unicode[STIX]{x1D6FD}_{\text{c}}$ is the inverse Berezinskii–Kosterlitz–Thouless critical temperature for superfluidity. The result is valid in the dilute limit $a^{2}\unicode[STIX]{x1D70C}\ll 1$ and if $\unicode[STIX]{x1D6FD}\unicode[STIX]{x1D70C}\gtrsim 1$.

Type
Mathematical Physics
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
© The Author(s) 2020

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