Twisted boundary conditions of quantum spin chains near the Gaussian fixed points

Abstract

Duality transformation, which relates a high-temperature phase to a\nlow-temperature one, is used exactly to determine the critical point for\nseveral models (2D Ising, Potts, Ashkin-Teller, 8-vertex), as the self dual\ncondition. By changing boundary condition, numerically we can determine the\nself-dual(critical) point of the Ashkin-Teller(or Gaussian) model. This is the\nfirst explicit application of the duality to the numerical calculation, with\nthe use of boundary conditions.\n