Logarithmic corrections to correlation decay in two-dimensional random-bond Ising systems.
The statistics of critical spin-spin correlation functions in Ising systems with nonfrustrated disorder are investigated on a strip geometry, via numerical transfer-matrix techniques. Conformal invariance concepts are used, in order to test for logarithmic corrections to pure power-law decay against distance. Fits of our data to conformal-invariance expressions, specific to logarithmic corrections to correlations on strips, give results with the correct sign, for the moments of order n = 0-4 of the correlation-function distribution. We find an interval of disorder strength along which corrections to pure-system behavior can be decomposed into the product of a known n -dependent factor and an approximately n -independent one, in accordance with predictions. A phenomenological fitting procedure is proposed, which takes partial account of subdominant terms of correlation-function decay on strips. In the low-disorder limit, it gives results in fairly good agreement with theoretical predictions, provided that an additional assumption is made.
Lessa
Jean C
JC
Departamento de Física, Universidade Estadual de Feira de Santana, Campus Universitário, 44031-460 Feira de Santana BA, Brazil. jean@if.ufrj.br
de Queiroz
S L A
SL