DYNAMICAL CORRELATION-FUNCTIONS OF THE S=1 2 NEAREST-NEIGHBOR AND HALDANE-SHASTRY HEISENBERG ANTIFERROMAGNETIC CHAINS IN ZERO AND APPLIED FIELDS/

We present a numerical diagonalization study of two one-dimensional S= 1/2 antiferromagnetic Heisenberg chains, having nearest-neighbor and H aldane-Shastry (1/r(2)) interactions, respectively. We have obtained t he T=0 dynamical correlation function, S-alpha alpha(q,omega), for cha ins of length N=8-28. We have studied S-zz(q,omega) for the Heisenberg chain in zero field, and from finite-size scaling we have obtained a limiting behavior that for large omega deviates from the conjecture pr oposed earlier by Muller ct al. For both chains we describe the behavi or of S-zz(q,omega) and S-xx(q,omega) for selected values of the appli ed held, and compare with previous work by Muller et al. and Talstra a nd Haldane. Suggestions for future finite-field neutron scattering exp eriments are made.