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Higher matrix-tree theorems and Bernardi polynomial
The classical matrix-tree theorem discovered by G.Kirchhoff in 1847
expresses the principal minor of the (n x n) Laplace matrix as a
sum of monomials of matrix elements indexed by directed trees with n
vertices. We prove, for any k >= n, a three-parameter family of
identities between degree k polynomials of matrix elements of the
Laplace matrix. For k=n and special values of the parameters the
identity turns to be the matrix-tree theorem.
For the same values of parameters and arbitrary k >= n the
left-hand side of the identity becomes a specific polynomial of the
matrix elements called higher determinant of the matrix. We study
properties of the higher determinants; in particular, they have an
application (due to M.Polyak) in the topology of 3-manifolds.