NUMERICAL INVESTIGATION OF CORRELATION-FUNCTIONS FOR THE UQSU(2) INVARIANT SPIN-1/2 HEISENBERG CHAIN

We consider the UqSU(2) invariant spin-1/2 xxz quantum spin chain at the roots of unity q = exp(i pi/(m + 1)), corresponding to different minimal models of conformal field theory. We conduct a numerical investigation of the correlation functions of UqSU(2) scalar two-point operators in order to find which operators in the minimal models they correspond to. Using graphical representations of the Temperley-Lieb algebra we are able to deal with chains of up to 28 sites. Depending on q, the correlation functions show different characteristics and finite-size behaviour. For m = 2/3, which corresponds to the Lee-Yang edge singularity, we find the surface and bulk critical exponent -1/5. Together with the known result in the case m = 3 (Ising model) this indicates that in the continuum limit the two-point operators involve conformal fields of spin m-1/m+1. For other roots of unity q the chains are too short to determine the surface and bulk critical exponents.