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Coexistence of long-range order for two observables at finite temperatures

N. Macris·C. -A. Piguet
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Abstract

We give a criterion for the simultaneous existence or non existence of two long-range orders for two observables, at finite temperatures, for quantum lattice many body systems. Our analysis extends previous results of G.-S. Tian limited to the ground state of similar models. The proof involves an inequality of Dyson-Lieb-Simon which connects the Duhamel two-point function to the usual correlation function. An application to the special case of the Holstein model is discussed.

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N. Macris, C. -A. Piguet. 1998-11-26. Coexistence of long-range order for two observables at finite temperatures. https://doi.org/10.1088/0305-4470%2F32%2F5%2F007

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