Integral and Theta Formulae for Solutions of Sl_N Knizhnik-Zamolodchikov Equations at Level Zero

The solutions of the sl_N Knizhnik-Zamolodchikov(KZ) equations at level 0 are studied. We present the integral formula which is obtained as a quasi-classical limit of the integral formula for form factors of the SU(N) invariant Thirring model due to F. Smirnov. A proof is given that those integrals satisfy sl_N KZ equation of level 0. The relation of the integral formulae with the chiral Szego kernel is clarified. As a consequence the integral formula with the special choice of cycles is rewritten in terms of the Riemann theta functions associated with the Z_N curve. This formula gives a generalization of Smirnov's formula for sl_2.