Multivariate polynomial graph invariants: dualities and critical properties.

We explore several types of functional relations on the family of multivariate Tutte polynomials: the Biggs duality and the star-triangle transformation at the critical point n=2. We deduce the Matiyasevich theorem and its inverse from the Biggs duality, apply the duality argument to construct the recursion on the parameter n. We provide two different proofs of the Zamolodchikov tetrahderon equation satisfied by the star-triangle transformation in the case of n=2 multivariate Tutte polynomial, extend the latter to the case of valency 2 points and show that the Biggs duality and the star-triangle transformation commute.