Villarreal's torsion-free quotient conjecture for uniform clutters

From papers

Let AA be a {0,1}\{0,1\}-matrix whose columns each contain the same number d2d\geq 2 of 11's, with column vectors v1,,vqv_1,\ldots,v_q. Let C\mathcal{C} be the clutter associated with AA, and let C\mathcal{C}' range over all minors of C\mathcal{C}. For each minor, let α0(C)\alpha_0(\mathcal{C}') be the smallest cardinality of a minimal vertex cover and let β1(C)\beta_1(\mathcal{C}') be the maximum number of pairwise independent edges. Villarreal's conjecture. If

α0(C)=β1(C)\alpha_0(\mathcal{C}')=\beta_1(\mathcal{C}')

for every minor C\mathcal{C}' of C\mathcal{C}, then

Zn+1/((v1,1),,(vq,1))\mathbb{Z}^{n+1}/\big((v_1,1),\ldots,(v_q,1)\big)

is torsion-free. The source describes this as a weaker conjecture following a proposition that reducedness of the associated graded ring forces the displayed quotient group to be torsion-free. Its resolution status is not given in the supplied text.

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Sources & referencesView supporting material

Primary source

I. Gitler, C. E. Valencia and R. H. Villarreal, “A note on Rees algebras and the MFMC property”, arXiv:math/0511307 (2007).

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