The Fundamental Fiber Sequence in etale Homotopy Theory

Haine, Peter J. and Holzschuh, Tim and Wolf, Sebastian (2024) The Fundamental Fiber Sequence in etale Homotopy Theory. INTERNATIONAL MATHEMATICS RESEARCH NOTICES, 2024 (1). pp. 175-196. ISSN 1073-7928, 1687-0247

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Abstract

Let k be a field with separable closure k & macr; superset of k, and let X be a qcqs k-scheme. We use the theory of profinite Galois categories developed by Barwick-Glasman-Haine to provide a quick conceptual proof that the sequences Pi(et)(<infinity)(X-k & macr;) -> Pi(et )(<infinity)(X) -> BGal(k & macr;/k) and Pi(et)(<infinity)(X-k & macr;) -> Pi(et)(<infinity)(X) -> BGal(k & macr;/k) of protruncated and profinite etale homotopy types are fiber sequences. This gives a common conceptual reason for the following two phenomena: first, the higher etale homotopy groups of X and the geometric fiber X-k & macr; are isomorphic, and second, if X-k & macr; is connected, then the sequence of profinite etale fundamental groups 1 -> pi circumflex expressionccent (et)(1) (X-k & macr;) -> pi circumflex expressionccent (et)(1)(X) -> Gal(k & macr;/k) -> 1 is exact. It also proves the analogous results for the groupe fondamental & eacute;largi of SGA3.

Item Type: Article
Uncontrolled Keywords: MODEL STRUCTURE
Subjects: 500 Science > 510 Mathematics
Divisions: Mathematics
Depositing User: Dr. Gernot Deinzer
Date Deposited: 20 Mar 2024 07:01
Last Modified: 04 Mar 2025 09:38
URI: https://pred.uni-regensburg.de/id/eprint/60015

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