2born (2born) wrote,

Что-то учебное для стат.физики

Может быть, когда-нибудь пригодится...

The Hellmann-Feynman theorem at finite temperature: https://arxiv.org/abs/1909.10298

We present a simple derivation of the Hellmann-Feynman theorem at finite temperature. We illustrate its validity by considering three relevant examples which can be used in quantum mechanics lectures: the one-dimensional harmonic oscillator, the one-dimensional Ising model and the Lipkin model. We show that the Hellmann-Feynman theorem allows one to calculate expectation values of operators that appear in the Hamiltonian. This is particularly useful when the total free-energy is available, but there is not direct access to the thermal average of the operators themselves.
Tags: Мегаучебник или Что я читал и похвалил, разгребая arXiv'ы

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