Indecomposable-module conjecture for Euler characteristics of crepant resolutions

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Let kk be an algebraically closed field of characteristic p>0p>0, and let G⊆SL(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:Y→Xf:Y\to X and f′:Y′→X′f':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.

References

Primary source

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

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