Department of Physics,

Ochanomizu University,

Ohtsuka 2-1-1, Bunkyo-ku,

Tokyo 112-8610,

JAPAN

E-mail: deguchi@phys.ocha.ac.jp

**The sl(2) loop algebra symmetry of the XXZ spin
chain: the Drinfeld polynomials of regular XXZ Bethe states**

**Abstract:**

We show that regular Bethe ansatz eigenvectors of the XXZ spin
chain at roots of unity are highest weight vectors and generate irreducible
representations of the $sl(2)$ loop algebra. Here the parameter $q*$*,
which is related to the XXZ anisotropy $\Delta$ through $\Delta=(q+1/q)/2$,
is given by a root of unity, $q$ to the $2N$th power equals to 1, for an
integer $N$.

See cond-mat/0503564.