Spectral function for the S=1 Heisenberg antiferromagetic chain

We study the spectral function S(k,ω) for the spin-1, one dimensional antiferromagnetic chain using a time-dependent density matrix renormalizaton group numerical method. We develop methods for extrapolating the time-dependent correlation functions to larger times in order to enhance the frequency resolution. The resulting spectral functions are impressively precise and accurate. Our results confirm many qualitative expectations from nonlinear σ model methods and test them quantitatively. The critical wave vector at which the single particle excitation emerges from the two-particle continuum is estimated to be 0.23π 0.24π .