Finite size emptiness formation probability of the XXZ spin chain at $\Delta=-1/2$

Abstract

In this paper we compute the Emptiness Formation Probability of a (twisted-) periodic XXZ spin chain of finite length at $\Delta=-1/2$, thus proving the formulae conjectured by Razumov and Stroganov \cite{raz-strog1, raz-strog2}. The result is obtained by exploiting the fact that the ground state of the inhomogeneous XXZ spin chain at $\Delta=-1/2$ satisfies a set of qKZ equations associated to $\displaystyle{U_q(\hat{sl_2})}$.