Pizzato–Sano–Tasin Frobenius bound for regular pairs

Let (d;a)(d;a) be a regular pair, with d=(d1,,dc)d=(d_1,\ldots,d_c) and a=(a0,,an)a=(a_0,\ldots,a_n), and define

δ(d;a)=i=1cdij=0naj.\delta(d;a)=\sum_{i=1}^c d_i-\sum_{j=0}^n a_j.

Assume that cnc\leq n and ai1a_i\neq 1 for every ii. Let F(a0,,an)F(a_0,\ldots,a_n) denote the Frobenius number of the weights.

Pizzato–Sano–Tasin conjecture. Then

δ(d;a)F(a0,,an).\delta(d;a)\geq F(a_0,\ldots,a_n).

This numerical conjecture translates effective non-vanishing for the relevant weighted complete intersections into a Frobenius-semigroup inequality. The paper proves the corresponding geometric result in codimension at most three; the conjecture is attributed to Tasin in the source.

Sources & referencesView supporting material

Primary source

Alessandro Passantino, “Effective non-vanishing for weighted complete intersections of low codimension”, arXiv:2501.13267 (2025).

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