Villarreal's torsion-free quotient conjecture for uniform clutters

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Let AA be a {0,1}\{0,1\}-matrix whose columns each contain the same number d≥2d\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.

References

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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