Lineshapes of dynamical correlation functions in Heisenberg chains - art. no. 174414

We calculate lineshapes of correlation functions by use of complete diagona lization data of finite chains and analytical implications from conformal-f ield theory, density of states, and Bethe ansatz. The numerical data have d ifferent finite-size accuracy in the cases of the imaginary and real parts in the frequency and time representations of spin-correlation functions, re spectively. The low-temperature, conformally invariant regime crosses over at T*approximate to0.7J to a diffusive regime that in turn connects continu ously to the high-temperature, interacting-fermion regime. The first-moment sum rule is determined.