Talk presented by Federico Berruto

Parallel Session: Spin Models II

Thursday July 1st, 16.40 - 17.00, Room B

Hadron spectrum and chiral symmetry breaking of the strongly coupled multiflavor $QCD_2$ from the Heisenberg spin chains: the large $N_c$ limit.

Abstract: We construct the effective Hamiltonians of the strongly coupled lattice N-flavor QCD_2 with N_c colors and we show their equivalence to a suitable SU(N) generalization of the quantum spin-N_c/2 antiferromagnetic Heisenberg model. We analyse in detail the N=2 model which is mapped onto the usual SU(2) spin-N_c/2 Heisenberg chain. We explicitly compute - in the 't Hooft limit $N_c\rightarrow \infty$- the mass spectrum of the lattice gauge model using a 1/S=2/N_c expansion. The low lying pions are the spinons of the Heisenberg chain while the massive excitations are created by applying to the ground state of the antiferromagnet suitable current operators generating charge transport. The mass spectrum of the strongly coupled lattice model is compared to the continuum results by means of Pade' approximants. We show also that the pattern of chiral symmetry breaking of the continuum theory is well reproduced in the lattice model.

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