$A_3$-formality for Demushkin groups at odd primes

Fuente: arXiv
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Main Authors: Pál, Ambrus, Quick, Gereon
Format: Preprint
Published: 2026
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author Pál, Ambrus
Quick, Gereon
author_facet Pál, Ambrus
Quick, Gereon
contents We study a weak form of formality for differential graded algebras, called $A_3$-formality, for the cohomology of pro-p Demushkin groups at odd primes p. We show that the differential graded $\mathbb{F}_p$-algebras of continuous cochains of Demushkin groups with q-invariant not equal 3 are $A_3$-formal, whereas Demushkin groups with q-invariant 3 are not $A_3$-formal. We prove these results by an explicit computation of the Benson-Krause-Schwede canonical class in Hochschild cohomology.
format Preprint
id arxiv_https___arxiv_org_abs_2601_07551
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle $A_3$-formality for Demushkin groups at odd primes
Pál, Ambrus
Quick, Gereon
Group Theory
Algebraic Topology
K-Theory and Homology
Number Theory
20J06, 12G05, 16E40, 18N40, 20E18, 55S30
We study a weak form of formality for differential graded algebras, called $A_3$-formality, for the cohomology of pro-p Demushkin groups at odd primes p. We show that the differential graded $\mathbb{F}_p$-algebras of continuous cochains of Demushkin groups with q-invariant not equal 3 are $A_3$-formal, whereas Demushkin groups with q-invariant 3 are not $A_3$-formal. We prove these results by an explicit computation of the Benson-Krause-Schwede canonical class in Hochschild cohomology.
title $A_3$-formality for Demushkin groups at odd primes
topic Group Theory
Algebraic Topology
K-Theory and Homology
Number Theory
20J06, 12G05, 16E40, 18N40, 20E18, 55S30
url https://arxiv.org/abs/2601.07551