On Euler Characteristic of equivariant sheaves

Alexander Braverman

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On Euler Characteristic of equivariant sheaves

Alexander Braverman

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Abstract

Let $k$ be an algebraically closed field of characteristic $p>0$ and let $\ell$ be another prime number. O. Gabber and F. Loeser proved that for any algebraic torus $T$ over $k$ and any perverse $\ell$-adic sheaf $\calF$ on $T$ the Euler characteristic $χ(\calF)$ is non-negative. We conjecture that the same result holds for any perverse sheaf $\calF$ on a reductive group $G$ over $k$ which is equivariant with respect to the adjoint action. We prove the conjecture when $\calF$ is obtained by Goresky-MacPherson extension from the set of regular semi-simple elements in $G$. From this we deduce that the conjecture holds for $G$ of semi-simple rank 1.

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Alexander Braverman. 2002-02-18. On Euler Characteristic of equivariant sheaves. https://arxiv.org/abs/math/0202165

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