Preprint
Sep 2026
Persistence of BKT phase transition in the 2D nonanalytic XY model
We study the two-dimensional XY model with the nonanalytic pair potential $2[(1-\cos\delta)/2]^{p}$, whose small-angle law $\propto|\delta|^{2p}$ carries a cusp for $p<1$ and a flat bottom for $p>1$, invalidating the harmonic spin-wave expansion. Two questions arise: the nature of the low-temperature ($T$) phase and of...
Si-Han Hu, Xian Pan, Kun Chen et al.
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