Indecomposable-module conjecture for Euler characteristics of crepant resolutions

Let kk be an algebraically closed field of characteristic p>0p>0, and let GSL(n,k)G\subseteq \mathrm{SL}(n,k) be a finite small group of finite representation type, meaning that there are finitely many isomorphism classes of indecomposable kGkG-modules. Let PP be a pp-Sylow subgroup of GG. Suppose that both

X:=Akn/GX:=\mathbb{A}^n_k/G

and

X:=Akn/PX':=\mathbb{A}^n_k/P

have crepant resolutions f:YXf:Y\to X and f:YXf':Y'\to X'. Indecomposable-module conjecture. Then

e(Y)=#Indk(G).e(Y)=\#\mathrm{Ind}_k(G).

This conjectures that the number of isomorphism classes of indecomposable kGkG-modules gives the algebraic invariant corresponding to the Euler characteristic of a crepant resolution in positive characteristic. The result is motivated by the main theorem for groups with a non-modular abelian normal subgroup of index pp, while the assertion remains open in the stated generality.

Sources & referencesView supporting material

Primary source

Linghu Fan, “Euler characteristic of crepant resolutions of specific modular quotient singularities”, arXiv:2411.18113 (2025).

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