Criticality in self-dual sine-Gordon models
P. Lecheminant, A. O. Gogolin, A. A. Nersesyan
TL;DR
This work addresses criticality in the self-dual extension of the sine-Gordon model at $\beta^2 = 2\pi N$, focusing on the non-perturbative $N=3$ case where a $\mathbb{Z}_3$ (three-state Potts) critical point is predicted. It develops two independent non-perturbative routes to the IR fixed point for $\beta^2 = 6\pi$: (i) an exact mapping to an integrable deformation of the $\mathbb{Z}_4$ parafermion CFT that exhibits a massless flow to the $\mathcal{M}_5$ (Potts) fixed point, and (ii) a relationship to a chirally asymmetric $\mathrm{su}(2)_4 \otimes \mathrm{su}(2)_1$ WZW model with anisotropic current-current interactions leading to a Toulouse decoupling point and the same $\mathbb{Z}_3$ IR physics. The paper also develops a complementary chirally stabilized liquids perspective, showing how the IR Potts criticality emerges from a massless flow in the anisotropic WZW framework, and discusses UV–IR transmutations of operators. These results solidify the connection between SDSG criticality and $\mathbb{Z}_3$ universality, with implications for two-dimensional XY systems with $N$-fold symmetry breaking and for one-dimensional quantum spin/electron systems.
Abstract
We discuss the nature of criticality in the $β^2 = 2 πN$ self-dual extention of the sine-Gordon model. This field theory is related to the two-dimensional classical XY model with a N-fold degenerate symmetry-breaking field. We briefly overview the already studied cases $N=2,4$ and analyze in detail the case N=3 where a single phase transition in the three-state Potts universality class is expected to occur. The Z$_3$ infrared critical properties of the $β^2 = 6 π$ self-dual sine-Gordon model are derived using two non-perturbative approaches. On one hand, we map the model onto an integrable deformation of the Z$_4$ parafermion theory. The latter is known to flow to a massless Z$_3$ infrared fixed point. Another route is based on the connection with a chirally asymmetric, su(2)$_4$ $\otimes$ su(2)$_1$ Wess-Zumino-Novikov-Witten model with anisotropic current-current interaction, where we explore the existence of a decoupling (Toulouse) point.
