Form factors of the XXZ Heisenberg spin-1/2 finite chain

Form factors for local spin operators of the XXZ Heisenberg spin-1/2 finite chain are computed. Representation theory of Drinfel'd twists in terms of F-matrices for the quantum affine algebra U-q((s) over cap l2) in finite-di mensional modules is used to calculate scalar products of two states involv ing one Bethe state (leading to Gaudin formula) and to solve the quantum in verse problem for local spin operators in the finite chain. Hence, we obtai n the representation of the n-spin correlation functions in terms of expect ation values (in ferromagnetic reference state) of the operator entries of the quantum monodromy matrix satisfying Yang-Baxter algebra. This leads to the direct calculation of the form factors of the XXZ Heisenberg spin-1/2 f inite chain as determinants of usual functions of the parameters of the mod el. A two-point correlation function for adjacent sites is also derived usi ng similar techniques. (C) 1999 Elsevier Science B.V. All rights reserved.