Breakdown of the perturbative renormalization group for S >= 1 random antiferromagnetic spin chains - art. no. 052414

We investigate the application of a perturbative renormalization group (RG) method to random antiferromagnetic Heisenberg chains with arbitrary spin s ize. At zero temperature we observe that initial arbitrary probability dist ributions develop a singularity at J=0, for all values of spin S. When the RG method is extended to finite temperatures, without any additional assump tions, we find anomalous results for S greater than or equal to1. These res ults lead us to conclude that the perturbative scheme is not adequate to st udy random chains with S greater than or equal to1. Therefore a random sing let phase in its more restrictive definition is only assured for spin-1/2 c hains.