Trailing Betti numbers for S^e(2,n)

Fix the multiplicity ee and write βj(a,b):=βj(Se(a,b))\beta_j(a,b):=\beta_j(S^e(a,b)). Trailing Betti-number conjecture for S^e(2,n). For n6n\geq 6,

βj(2,n)=βj(2,3)for all jn5,\beta_j(2,n)=\beta_j(2,3)\quad\text{for all }j\leq n-5,

and

βn4(2,n)=βn4(2,3)+1.\beta_{n-4}(2,n)=\beta_{n-4}(2,3)+1.

Moreover, Se(2,e1)S^e(2,e-1) is conjectured to be the closest to being Gorenstein in this family, with

βj(2,e1)={βj(2,3),je6,βj(2,3)+1,j=e5,βj(2,3)+3,j=e4,βj(2,3)+2=3,j=e3.\beta_j(2,e-1)=\begin{cases}\beta_j(2,3),&j\leq e-6,\beta_j(2,3)+1,&j=e-5,\beta_j(2,3)+3,&j=e-4,\beta_j(2,3)+2=3,&j=e-3.\end{cases}

The claim compares the Betti sequences with those of the Gorenstein case Se(2,3)S^e(2,3); no resolution status is supplied in the text.

Sources & referencesView supporting material

Primary source

Kriti Goel, Nil Şahin, Srishti Singh and Hema Srinivasan, “Numerical Semigroups of Sally Type II”, arXiv:2512.10812 (2025).

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