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arXiv · 1808.09212

Spontaneous symmetry breaking in coupled Bose-Einstein condensates

Hal Tasaki
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Abstract

We study a system of two hardcore bosonic Hubbard models weakly coupled with each other by tunneling. Assuming that the single uncoupled model exhibits off-diagonal long-range order, we prove that the coupled system exhibits spontaneous symmetry breaking (SSB) in the infinite volume limit, in the sense that the two subsystems maintain a definite relative U(1) phase when the tunneling is turned off. Although SSB of the U(1) phase is never observable in a single system, SSB of the relative U(1) phase is physically meaningful and observable by interference experiments. The present theorem is made possible by the rigorous theory of low-lying states and SSB in quantum antiferromagnets developed over the years.

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Hal Tasaki. 2018-08-28. Spontaneous symmetry breaking in coupled Bose-Einstein condensates. https://doi.org/10.1007/s10955-019-02435-9

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