COMPUTATION OF DYNAMICAL STRUCTURE FACTORS WITH THE RECURSION METHOD

We compute the energies and transition probabilities for low excitatio ns in the one-dimensional antiferromagnetic spin-1/2 Heisenberg model by means of the recursion method. We analyse finite-size effects in th e Euclidean time (tau-) representation and compare the resulting estim ate for the thermodynamical limit with two parametrizations for the dy namical structure factors in the spectral (omega-) representation.