Spectral sum rules of the Dirac operator and partially quenched chiral condensates

Abstract

Exploiting Virasoro constraints on the effective finite-volume partition function, we derive generalized Leutwyler–Smilga spectral sum rules of the Dirac operator to high order. By introducing N v fermion species of equal masses, we next use the Virasoro constraints to compute two (low-mass and large-mass) expansions of the partially quenched chiral condensate through the replica method of letting N v →0. The low-mass expansion can only be pushed to a certain finite order due to de Wit–'t Hooft poles, but the large-mass expansion can be carried through to arbitrarily high order. Results agree exactly with earlier results obtained through both Random Matrix Theory and the supersymmetric method.