M. Distasio et al., FINITE-TEMPERATURE RESULTS FROM CONSTRAINED FERMIONIZATION IN THE 2-DSPIN 1 2 HEISENBERG-ANTIFERROMAGNET .1. THE NEEL PHASE/, International journal of modern physics b, 8(6), 1994, pp. 741-756
The antiferromagnetic saddle point is studied up to one-loop correctio
ns, including, within the same approximation, the constraint of single
site occupancy in the fermionization procedure, at all temperatures.
The resulting spin wave spectrum and zero point fluctuations are the s
ame as those of the spin wave theory. The effect of the constraint on
the temperature dependence of the specific heat is discussed.