Integral-group and Ehrhart characterization conjecture for uniform clutters

Let C\mathcal C be a uniform clutter with edge incidence vectors v1,,vqv_1,\ldots,v_q, and suppose its packing property holds. Define

B=((v1,1),,(vq,1))B=((v_1,1),\ldots,(v_q,1))

as the matrix whose columns are the augmented vectors, let rr be the rank of BB, let Δr(B)\Delta_r(B) be the corresponding determinantal divisor, and set

P=conv(v1,,vq).P=\operatorname{conv}(v_1,\ldots,v_q).

Here K[Ft]\overline{K[Ft]} is the integral closure of the homogeneous ring K[Ft]K[Ft], and A(P)A(P) is the Ehrhart ring of PP. Integral-group and Ehrhart characterization conjecture. If C\mathcal C is a uniform clutter with the packing property, then all of the following equivalent conditions hold: (a) Zn+1/((v1,1),,(vq,1))\mathbb{Z}^{n+1}/((v_1,1),\ldots,(v_q,1)) is a free group; (b) Δr(B)=1\Delta_r(B)=1; (c) BB diagonalizes over Z\mathbb{Z} to an identity matrix; and (d) K[Ft]=A(P)\overline{K[Ft]}=A(P). The source presents this as a consequence suggested by the preceding conjecture, but gives no resolution status.

Sources & referencesView supporting material

Primary source

Luis A. Dupont and Rafael H. Villarreal, “Algebraic and combinatorial properties of ideals and algebras of uniform clutters of TDI systems”, arXiv:0801.1478 (2009).

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