Correlation functions of the XXZ Heisenberg spin-1/2 chain in a magnetic field

Using the algebraic Bethe ansatz method, and the solution of the quantum in verse scattering problem for local spins, we obtain multiple integral repre sentations of the n-point correlation functions of the XXZ Heisenberg spin- 1/2 chain in a constant magnetic field. For zero magnetic field, this resul t agrees, in both the massless and massive (anti-ferromagnetic) regimes, wi th the one obtained from the q-deformed KZ equations (massless: regime) and the representation theory of the quantum affine algebra U-q(s (l) over cap (2)) together with the corner transfer matrix approach (massive regime). (C ) 2000 Elsevier Science B.V. All rights reserved.