DYNAMIC CORRELATIONS IN A CLASSICAL 2-DIMENSIONAL HEISENBERG-ANTIFERROMAGNET - REPLY

In a recent publication [Wysin and Bishop, Phys. Rev. B 42, 810 (1990)], we incorrectly derived the condition that the wave-vector- and time-dependent dynamic structure function S(q,t) for isotropic Heisenberg magnets should satisfy dS(q,t)/dt\t=0 = 0. In the preceding Comment by Brown, it has been pointed out that the derivation did not preserve the spin commutation relations. However, the above quantity is correctly determined by a sum of three-point spin correlations, [SnxSmySmz], which we show are all identically zero in any number of space dimensions. Therefore, the condition is valid, and indeed implies that a sum of Lorentzians cannot be used to fit the frequency-dependent dynamic correlation function S (q,omega).