$Φ^4_2$ theory limit of a many-body bosonic free energy

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Autori principali: Jougla, Lucas, Rougerie, Nicolas
Natura: Preprint
Pubblicazione: 2025
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author Jougla, Lucas
Rougerie, Nicolas
author_facet Jougla, Lucas
Rougerie, Nicolas
contents We consider the quantum Gibbs state of an interacting Bose gas on the 2D torus. We set temperature, chemical potential and coupling constant in a regime where classical field theory gives leading order asymptotics. In the same limit, the repulsive interaction potential is set to be short-range: it converges to a Dirac delta function with a rate depending polynomially on the other scaling parameters. We prove that the free-energy of the interacting Bose gas (counted relatively to the non-interacting one) converges to the free energy of the $Φ^4_2$ non-linear Schrödinger-Gibbs measure, thereby revisiting recent results and streamlining proofs thereof. We combine the variational method of Lewin-Nam-Rougerie to connect, with controled error, the quantum free energy to a classical Hartree-Gibbs one with smeared non-linearity. The convergence of the latter to the $Φ^4_2$ free energy then follows from arguments of Fröhlich-Knowles-Schlein-Sohinger. This derivation parallels recent results of Nam-Zhu-Zhu.
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id arxiv_https___arxiv_org_abs_2512_10704
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle $Φ^4_2$ theory limit of a many-body bosonic free energy
Jougla, Lucas
Rougerie, Nicolas
Analysis of PDEs
Quantum Gases
Mathematical Physics
We consider the quantum Gibbs state of an interacting Bose gas on the 2D torus. We set temperature, chemical potential and coupling constant in a regime where classical field theory gives leading order asymptotics. In the same limit, the repulsive interaction potential is set to be short-range: it converges to a Dirac delta function with a rate depending polynomially on the other scaling parameters. We prove that the free-energy of the interacting Bose gas (counted relatively to the non-interacting one) converges to the free energy of the $Φ^4_2$ non-linear Schrödinger-Gibbs measure, thereby revisiting recent results and streamlining proofs thereof. We combine the variational method of Lewin-Nam-Rougerie to connect, with controled error, the quantum free energy to a classical Hartree-Gibbs one with smeared non-linearity. The convergence of the latter to the $Φ^4_2$ free energy then follows from arguments of Fröhlich-Knowles-Schlein-Sohinger. This derivation parallels recent results of Nam-Zhu-Zhu.
title $Φ^4_2$ theory limit of a many-body bosonic free energy
topic Analysis of PDEs
Quantum Gases
Mathematical Physics
url https://arxiv.org/abs/2512.10704