Abstract. We continue our investigation of the Baxter–Bazhanov–Stroganov or τ⁽²⁾-model using the method of separation of variables (von Gehlen et al 2006 J. Phys. A: Math. Gen. 39 7257, 2007 J. Phys. A: Math. Theor. 40 14117). In this paper we derive for the first time the factorized formula for form-factors of the Ising model on a finite lattice conjectured previously by Bugrij and Lisovyy (2003 Phys. Lett. A 319 390, 2003 J. Theor. Math. Phys. 140 987). We also find the matrix elements of the spin operator for the finite quantum Ising chain in a transverse field.

Dedicated to Professor Anatoly Bugrij on the occasion of his 60-th birthday

PACS numbers: 75.10.Hk, 75.10.Jm, 05.50.+q, 02.30.Ik

Print publication: Issue 9 (7 March 2008)
Received 10 December 2007, in final form 20 January 2008
Published 19 February 2008