Non-orientable representation spheres

Sam K. Miller

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arXiv · 2608.18015

Non-orientable representation spheres

Sam K. Miller

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Abstract

For any finite group, we pose the following question: given an irreducible real representation, is the associated representation sphere non-orientable if and only if the representation is nontrivial of real type? We prove that the answer to this question is yes if the group has a normal Sylow 2-subgroup, but exhibit a 2-nilpotent group of order 112 for which the answer is no via elementary arguments. We also link the question to the unit group of the Burnside ring, where we recover a basis discovered by Bouc for 2-groups, and pose a conjecture about detection of non-orientability from solvable subgroups. The question is motivated by issues arising from the construction of permutation twisted cohomology for finite groups.

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Sam K. Miller. 2026-08-18. Non-orientable representation spheres. https://arxiv.org/abs/2608.18015

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