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 the low temperature specificheat density scales as exp(-2J/T), corresponding to an``effective'' gap of size 2J; in addition, an associated cross-overlength scale grows as exp(J/T). We justify these scalings viathe degeneracy of the low-lying excitations and by the way low energydomain walls proliferate in this model.