Merino–Welsh conjectures for matroids

Let MM be a matroid without loops and coloops, and let TM(x,y)T_M(x,y) denote its Tutte polynomial.

Merino–Welsh conjectures. The following three inequalities should hold:

max(TM(2,0),TM(0,2))TM(1,1),\max\left(T_M(2,0),T_M(0,2)\right)\geq T_M(1,1), TM(2,0)+TM(0,2)2TM(1,1),T_M(2,0)+T_M(0,2)\geq 2T_M(1,1), TM(2,0)TM(0,2)TM(1,1)2.T_M(2,0)T_M(0,2)\geq T_M(1,1)^2.

These are respectively the maximum, additive, and multiplicative versions of the graph conjecture. The multiplicative inequality implies the additive one, which implies the maximum inequality. The conjectures are known for several classes, including lattice path matroids and paving matroids for the additive version, while the general matroidal claims remain open.

Sources & referencesView supporting material

Primary source

Luis Ferroni and Benjamin Schröter, “The Merino–Welsh conjecture for split matroids”, arXiv:2204.07132 (2022).

Additional references

2 papers in this index state this conjecture (2021–2022). The statement above is taken from the most recent of them; the others are arXiv:2105.01825.

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