Logarithmic corrections to correlation decay in two-dimensional random-bond Ising systems

TL;DR

This paper investigates the critical spin-spin correlations in two-dimensional random-bond Ising systems, revealing logarithmic corrections to pure power-law decay and confirming theoretical predictions through numerical transfer-matrix analysis.

Contribution

It provides numerical evidence for logarithmic corrections to correlation decay in disordered Ising systems and introduces a phenomenological fitting method that accounts for subdominant decay terms.

Findings

Logarithmic corrections are confirmed in correlation functions.

Disorder effects can be decomposed into n-dependent and n-independent factors.

The phenomenological model aligns with theoretical predictions in low-disorder regimes.

Abstract

The statistics of critical spin-spin correlation functions in Ising systems with non-frustrated 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.