2008Unpublished venueRequires access

The characteristic class and ramification of an ℓ-adic étale sheaf

Ahmed Abbes, Takeshi Saito

Open publisher page 19 citations

Abstract

We introduce the characteristic class of an l-adic etale sheaf using a cohomological pairing due to Verdier (SGA5). As a consequence of the Lefschetz-Verdier trace formula, its trace computes the Euler-Poincare characteristic of the sheaf. We compare the characteristic class to two other invariants arising from ramification theory. One is the Swan class of Kato-Saito (math.AG/0402010) and the other is the 0-cycle class defined by Kato for rank 1 sheaves.

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What this paper is about

We introduce the characteristic class of an l-adic etale sheaf using a cohomological pairing due to Verdier (SGA5). As a consequence of the Lefschetz-Verdier trace formula, its trace computes the Euler-Poincare characteristic of the sheaf. We compare the characteristic class to two other invariants arising from ramification theory. One is the Swan class of Kato-Saito (math.AG/0402010) and the other is the 0-cycle class defined by Kato for rank 1 sheaves.

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Available abstract

We introduce the characteristic class of an l-adic etale sheaf using a cohomological pairing due to Verdier (SGA5). As a consequence of the Lefschetz-Verdier trace formula, its trace computes the Euler-Poincare characteristic of the sheaf. We compare the characteristic class to two other invariants arising from ramification theory. One is the Swan class of Kato-Saito (math.AG/0402010) and the other is the 0-cycle class defined by Kato for rank 1 sheaves.

Key concepts: Mathematics, Sheaf, Pure mathematics, TRACE (psycholinguistics), Class (philosophy), Ramification, Rank (graph theory), Euler characteristic

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