万源 Spontaneous breaking of continuous symmetry in two dimensions under shear flow 2022/03/30

The celebrated Mermin-Wagner theorem states that continuous symmetries cannot break spontaneously in two-dimensional statistical models with short-range interactions. In this talk, I shall examine how this theorem may be evaded under nonequilibrium conditions following the elegant work from Nakano and coauthors [1]. I will begin with a quick review of the usual infrared catastrophe argument that leads to the Mermin-Wagner theorem. Then, I will show that the catastrophe is removed by an infinitesimal shear flow. As a result, a sheared O(N) model should exhibit a finite-temperature phase transition. Finally, I will present numerical simulations in support of this argument and comments on some open problems.

[1] Hiroyoshi Nakano, Yuki Minami, and Shin-ichi Sasa, Physical Review Letters 126, 160604 (2021); arXiv:2011.06256


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