Poster presented by Gianluca Grignani
Topic: Spin Models
Lattice Gauge Theories and the Heisenberg Antiferromagnetic Chain
Abstract: It is shown that the ground states of the strongly coupled 2-flavor lattice Schwinger model and of the 1-flavor QCD_2 with SU(N_c=2) gauge group are both given by the ground state of the spin 1/2 Heisenberg antiferromagnetic chain. The low lying spectrum of both the gauge theories is determined: the massless excitations are identified with the excitations of the Heisenberg model, and the mass gaps of the massive excitations are computed in terms of correlators of the Heisenberg model. A satisfactory agreement with the results of the continuum theory, already at the second order in the strong coupling expansion, is found. It is shown that the pattern of symmetry breaking of the continuum theory is well reproduced by the lattice theory. Contrary to what happens in the large N_c limit, in the SU(2)-QCD_2 the chiral condensate vanishes.