Critical points of coupled vector-Ising systems. Exact results

Authors

Gesualdo Delfino; Noel Lamsen

Source

J. Phys. A. Math. Theor. 52, 35LT02 (2019). DOI: 10.1088/1751-8121/ab3055

Preprint

arXiv:1902.09901

Abstract

We show that scale-invariant scattering theory allows to exactly determine the critical points of two-dimensional systems with coupled O(N) and Ising order parameters. The results are obtained for N continuous and include criticality of the loop gas type. In particular, for N = 1 we exhibit three critical lines intersecting at the Berezinskii-Kosterlitz-Thouless transition point of the Gaussian model and related to the Z₄ symmetry of the isotropic Ashkin-Teller model. For N = 2 we classify the critical points that can arise in the XY-Ising model and provide exact answers about the critical exponents of the fully frustrated XY model.