Abstract
It is numerically shown that the discontinuous character of the helicity modulus of the two-dimensional XY model at the Kosterlitz-Thouless (KT) transition can be directly related to a higher-order derivative of the free energy without presuming any a priori knowledge of the nature of the transition. It is also suggested that this higher-order derivative is of intrinsic interest in that it gives an additional characteristic of the KT transition which might be associated with a universal number akin to the universal value of the helicity modulus at the critical temperature.
- Received 11 December 2002
DOI:https://doi.org/10.1103/PhysRevB.67.172509
©2003 American Physical Society