Antiferromagnetic 4-d O(4) Model

Abstract

We study the phase diagram of the four dimensional O(4) model with first (beta1) and second (beta2) neighbor couplings, specially in the beta2 < 0 region, where we find a line of transitions which seems to be second order. We also compute the critical exponents on this line at the point beta1 =0 (F4 lattice) by Finite Size Scaling techniques up to a lattice size of 24, being these exponents different from the Mean Field ones.

Comments: 26 pages LaTeX2e, 7 figures. The possibility of logarithmic corrections has been considered, new figures and tables added. Accepted for publication in Physical Review D