Temperature dependence of universal fluctuations in the two-dimensional harmonic XY model.
We compute exact analytical expressions for the skewness and kurtosis in the two-dimensional harmonic XY model. These quantities correspond to the third and fourth normalized moments of the probability density function (PDF) of the magnetization of the model. From their behavior, we conclude that they depend explicitly on the system temperature even in the thermodynamic limit, and hence the PDF itself must depend on it. Our results correct the hypothesis called universal fluctuations, they confirm and extend previous results which showed a T dependence of the PDF, including perturbative expansions within the XY model up to first order in temperature.
Palma
G
G
Departamento de Física, Universidad de Santiago de Chile, Casilla 307, Santiago 2, Chile. gpalma@usach.cl