paper

Quantum fluctuations in quantum lattice-systems with continuous symmetry

arXiv:cond-mat/9602138 · doi:10.1007/BF02175562

Abstract

We discuss conditions for the absence of spontaneous breakdown of continuous symmetries in quantum lattice systems at . Our analysis is based on Pitaevskii and Stringari's idea that the uncertainty relation can be employed to show quantum fluctuations. For the one-dimensional systems, it is shown that the ground state is invariant under the continuous transformation if a certain uniform susceptibility is finite. For the two- and three-dimensional systems, it is shown that truncated correlation functions cannot decay any more rapidly than whenever the continuous symmetry is spontaneously broken. Both of these phenomena occur owing to quantum fluctuations. Our theorems cover a wide class of quantum lattice-systems having not-too-long-range interactions.

14 pages. To appear in J.Stat.Phys

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