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Polymatroid Tutte Polynomial


The polymatroid Tutte polynomial is an activity generating polynomial for the integer bases of an integral polymatroid. Fix a total order on its ground set E, let B be its set of integer bases, and let e_i denote the coordinate unit vector at i. For a basis b, an element i is internally active if b-e_i+e_j not in B for every j<i, and externally active if b+e_i-e_j not in B for every j<i. Writing a(b), c(b), and s(b) for the numbers of only internally active, only externally active, and simultaneously active elements gives

 T_B(x,y)=sum_(b in B)x^(a(b))y^(c(b))(x+y-1)^(s(b)).

The polynomial is independent of the chosen total order (Tóthmérész 2026).

For a matroid of rank r on m elements, this normalization is related to its ordinary Tutte polynomial T_M by

 T_B(x,y)=x^(m-r)y^rT_M((x+y-1)/y,(x+y-1)/x).

The right side is interpreted as the polynomial obtained after cancellation, including when x or y is zero. For example, one element with one integer basis gives T_B(x,y)=x+y-1.

Tóthmérész (2026) proves that computation-tree activities, using either a minimum or a maximum rule, also yield this polynomial. The hypergraph Tutte polynomial is a special case using the integer bases supplied by a connected hypergraph.


See also

Hypergraph Tutte Polynomial, Matroid, Polymatroid, Tutte Polynomial

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References

Tóthmérész, L. "The Two-Variable Hypergraph Tutte Polynomial via Embedding Activities and Computation-Tree Activities." Elec. J. Combin. 33, P4.7, 2026. https://doi.org/10.37236/13306.

Cite this as:

Weisstein, Eric W. "Polymatroid Tutte Polynomial." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/PolymatroidTuttePolynomial.html

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