Upper Bounds on the Torsion Index of Half-Spin Groups

Fuente: arXiv
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Auteurs principaux: Baek, Sanghoon, Devyatov, Rostislav
Format: Preprint
Publié: 2025
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author Baek, Sanghoon
Devyatov, Rostislav
author_facet Baek, Sanghoon
Devyatov, Rostislav
contents The torsion index of split simple groups has been extensively studied, notably by Totaro, who calculated the torsion indexes of the spin groups and $E_{8}$ in [5] and [6], respectively. The aim of this paper is to provide upper bounds for the torsion index of half-spin groups, the only remaining case in the calculation of torsion indexes for split simple groups. We present general upper bounds for the torsion index of half-spin groups, showing that, except for certain exceptional cases, it is at most twice that of the corresponding spin groups. For these exceptional cases, the torsion index is bounded above by at most $2^3$ times that of the spin groups. Our results also reveal that in many cases, the torsion index of half-spin groups coincides with that of the spin groups.
format Preprint
id arxiv_https___arxiv_org_abs_2505_06705
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Upper Bounds on the Torsion Index of Half-Spin Groups
Baek, Sanghoon
Devyatov, Rostislav
Algebraic Geometry
K-Theory and Homology
20G15, 14N15 (primary), 57T15 (secondary)
The torsion index of split simple groups has been extensively studied, notably by Totaro, who calculated the torsion indexes of the spin groups and $E_{8}$ in [5] and [6], respectively. The aim of this paper is to provide upper bounds for the torsion index of half-spin groups, the only remaining case in the calculation of torsion indexes for split simple groups. We present general upper bounds for the torsion index of half-spin groups, showing that, except for certain exceptional cases, it is at most twice that of the corresponding spin groups. For these exceptional cases, the torsion index is bounded above by at most $2^3$ times that of the spin groups. Our results also reveal that in many cases, the torsion index of half-spin groups coincides with that of the spin groups.
title Upper Bounds on the Torsion Index of Half-Spin Groups
topic Algebraic Geometry
K-Theory and Homology
20G15, 14N15 (primary), 57T15 (secondary)
url https://arxiv.org/abs/2505.06705