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arXiv · 2505.23136

The second order Huang-Yang approximation to the Fermi thermodynamic pressure

Xuwen Chen·Jiahao Wu·Zhifei Zhang
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Abstract

We consider a dilute Fermi gas in the thermodynamic limit with interaction potential scattering length $\mathfrak{a}_0$ at temperature $T>0$. We prove the 2nd order Huang-Yang approximation for the Fermi pressure of the system, in which there is a 2nd order term carrying the positive temperature efffect.Our formula is valid up to the temperature $T<\rho^{\frac{2}{3}+\frac{1}{6}}$, which is, by scaling, also necessary for the Huang-Yang formula to hold. Here, $T_F\sim\rho^{\frac{2}{3}}$ is the Fermi temperature. We also establish during the course of the proof, a conjecture regarding the second order approximation of density $\rho$ by R. Seiringer \cite{FermithermoTpositive}. Our proof uses frequency localization techniques from the analysis of nonlinear PDEs and does not involve spatial localization or Bosonization. In particular, our method covers the classical Huang-Yang formula at zero temperature.

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Xuwen Chen, Jiahao Wu, Zhifei Zhang. 2025-05-29. The second order Huang-Yang approximation to the Fermi thermodynamic pressure. https://arxiv.org/abs/2505.23136

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