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Group representations in the homology of 3-manifolds

Abstract : If M is a manifold with an action of a group G, then the homology group H_1(M,Q) is naturally a Q[G]-module, where Q[G] denotes the rational group ring. We prove that for every finite group G, and for every Q[G]-module V, there exists a closed hyperbolic 3-manifold M with a free G-action such that the Q[G]-module H_1(M,Q) is isomorphic to V. We give an application to spectral geometry: for every finite set P of prime numbers, there exist hyperbolic 3-manifolds N and N' that are strongly isospectral such that for all p in P, the p-power torsion subgroups of H_1(N,Z) and of H_1(N',Z) have different orders. We also show that, in a certain precise sense, the rational homology of oriented Riemannian 3-manifolds with a G-action "knows" nothing about the fixed point structure under G, in contrast to the 2-dimensional case. The main geometric techniques are Dehn surgery and, for the spectral application, the Cheeger-M\"uller formula, but we also make use of tools from different branches of algebra, most notably of regulator constants, a representation theoretic tool that was originally developed in the context of elliptic curves.
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Contributor : Aurel Page Connect in order to contact the contributor
Submitted on : Friday, December 22, 2017 - 3:37:35 PM
Last modification on : Tuesday, October 19, 2021 - 11:06:00 PM

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Alex Bartel, Aurel Page. Group representations in the homology of 3-manifolds. Commentarii Mathematici Helvetici, European Mathematical Society, 2019, ⟨10.4171/CMH/455⟩. ⟨hal-01671748⟩



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