Width bound and equality characterization for the defining ideal of a numerical semigroup tangent cone

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Let HH be a numerical semigroup, let IH∗I_H^* denote the defining ideal of its tangent cone, let μ(H)\mu(H) be the number of minimal generators of HH, and let \width(H)\width(H) be the difference between the largest and smallest generators in a minimal generating set of HH. Width bound conjecture.

μ(IH∗)≤(\width(H)+12).\mu(I_H^*) \leq {\width(H)+1 \choose 2}.

If μ(H)≥2\mu(H) \geq 2, equality holds if and only if there exist integers w,k≥1w,k \geq 1 such that

H=⟨kw+1,kw+2,…,(k+1)w+1⟩.H=\langle kw+1,kw+2,\dots,(k+1)w+1\rangle.

This conjecture would give an explicit bound in terms of the width for the number of minimal generators of the tangent-cone defining ideal, refining the uniform boundedness established in the preceding corollary. The source reports that computer calculations suggest the statement; no proof or resolution is provided here.

References

Primary source

Jürgen Herzog and Dumitru I. Stamate, “On the defining equations of the tangent cone of a numerical semigroup ring”, arXiv:1308.4644 (2014).

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