A. Varchenko, CRITICAL-POINTS OF THE PRODUCT OF POWERS OF LINEAR FUNCTIONS AND FAMILIES OF BASES OF SINGULAR VECTORS, Compositio mathematica, 97(3), 1995, pp. 385-401
The quasiclassical asymptotics of the Knizhnik-Zamolodchikov equation
with values in the tenser product of sh representations are considered
. The first term of asymptotics is an eigenvector of a system of commu
ting operators. We show that the norm of this vector with respect to t
he Shapovalov form is equal to the determinant of the matrix of second
derivatives of a suitable function. This formula is an analog of the
Gaudin and Korepin formulae for the norm of the Bethe vectors. We show
that the eigenvectors form a basis under certain conditions.