Multiplicity bounds for \d835\dcb-Gorenstein toric varieties of rank r

Let XX be an nn-dimensional δ835\dcb\delta 835\dcb-Gorenstein toric variety of rank rr and Gorenstein index k2k\ge 2. Let QQ^\circ be the polar weight matrix defined in the source, and set r:=rkQr^\circ:=\operatorname{rk} Q^\circ and r:=max(r,r)r':=\max(r,r^\circ). Let tk,nt_{k,n} be the recursively defined sequence from the source, and let μn,r\mu_{n,r'} denote the McMullen number. Multiplicity-bound conjecture.

multX[2k(k+1)22+r]if n=2,\operatorname{mult} X\le \left[\frac{2k(k+1)^2}{2+r'}\right]\quad\text{if }n=2, multX[4tk,32(7+r)k]=[4k(k+1)2[k(k+1)+1]27+r]if n=3,\operatorname{mult} X\le \left[\frac{4t_{k,3}^2}{(7+r')k}\right]=\left[\frac{4k(k+1)^2\bigl[k(k+1)+1\bigr]^2}{7+r'}\right]\quad\text{if }n=3,

and

multX[2tk,n2knkμn,r]if n4.\operatorname{mult} X\le \left[\frac{2t_{k,n}^2k^n}{k\mu_{n,r'}}\right]\quad\text{if }n\ge 4.

These bounds are proposed as an extension of the corresponding bounds for fake weighted projective spaces from the preceding theorem to arbitrary Q\mathbb{Q}-Gorenstein toric varieties. The source presents them as plausible consequences of an extension of the cited anti-canonical self-intersection bounds, so their resolution is not established here.

Sources & referencesView supporting material

Primary source

Michele Rossi, “The multiplicity of a Mori Dream Space”, arXiv:2502.13507 (2025).

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