Critical thermodynamics of the two-dimensional +/-J Ising spin glass
Résumé
We compute the exact partition function of 2d Ising spin glasseswith binary couplings. In these systems, the ground state is highlydegenerate and is separated from the first excited state by a gap ofsize 4J. Nevertheless, we find that thelow temperature specific heat density scalesas exp(-2J/T), corresponding to an "effective" gap of size 2J; in addition, the associatedlength scale grows as exp(J/T). We justify these scalingsvia the degeneracy of the low lying excitations and bythe way low energy domain walls proliferate in this model.