Critical Behaviour of integrable mixed spins chains

Abstract

We construct a mixed spin 1/2 and $S$ integrable model and investigate its finite size properties. For a certain conformal invariant mixed spin system the central charge can be decomposed in terms of the conformal anomaly of two single integrable models of spin 1/2 and spin $(S-1/2)$. We also compute the ground state energy and the sound velocity in the thermodynamic limit.

This was the first correct calculation of the central charge in mixed integrable spin chains. For effects of a magnetic field see J.Phys.A:Math.Gen. 26 (1993) 7301