Coexistence of long-range order for two observables at finite temperatures
arXiv:cond-mat/9811376 · doi:10.1088/0305-4470/32/5/007
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.
12 pages, accepted for publication in J. of Phys. A