Abstract:We prove that if the group $\mathrm{SL}_2(\mathbb Z[1/p])$ is flexibly Hilbert--Schmidt stable for some prime $p$, then it admits a non-hyperlinear finite central extension. Consequently, a positive answer to the following question would yield an explicit example of a non-hyperlinear group: If two representations of the modular group $\mathrm{SL}_2(\mathbb{Z})$ almost agree on an Iwahori subgroup $B$, must they be close to representations that agree on $B$? More generally, we investigate spectral gap properties for asymptotic representations of higher rank lattices and groups with property (T:FD). In this setting, we prove that character rigidity is equivalent to a weak form of stability.
From: Alon Dogon [view email]
[v1]
Wed, 25 Jun 2025 21:27:27 UTC (64 KB)
[v2]
Tue, 23 Jun 2026 16:17:46 UTC (61 KB)
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