algebra / Geometric group theory; hyperbolic groups

Are all word-hyperbolic groups residually finite?

Theorem 1.1: there is a torsion-free word-hyperbolic group GG, the fundamental group of a finite Euclidean triangle complex, that is not residually finite; one member of a fixed finite family of nontrivial elements lies in the finite residual, without identifying which. Corollary 1.2: every finite-dimensional representation of GG over every commutative field kills the finite residual, so GG is linear over no field. With Kapovich-Wise this gives a nontrivial hyperbolic group with no nontrivial finite quotient and a hyperbolic group that is not virtually torsion-free (curator's reading of the paper's stated consequences). It says nothing about skew fields or infinite-dimensional representations, and does not settle whether all hyperbolic groups are sofic.

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algebraSep 23, 2026Significance 66/100Registry: lean checked

Are all word-hyperbolic groups residually finite?

Prior state unknown→disproved

Theorem 1.1: there is a torsion-free word-hyperbolic group GG, the fundamental group of a finite Euclidean triangle complex, that is not residually finite; one member of a fixed finite family of nontrivial elements lies in the finite residual, without identifying which. Corollary 1.2: every finite-dimensional representation of GG over every commutative field kills the finite residual, so GG is linear over no fiel…

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Theorem 1.1: there is a torsion-free word-hyperbolic group GG, the fundamental group of a finite Euclidean triangle complex, that is not residually finite; one member of a fixed finite family of nontrivial elements lies in the finite residual, without identifying which. Corollary 1.2: every finite-dimensional representation of GG over every commutative field kills the finite residual, so GG is linear over no field. With Kapovich-Wise this gives a nontrivial hyperbolic group with no nontrivial finite quotient and a hyperbolic group that is not virtually torsion-free (curator's reading of the paper's stated consequences). It says nothing about skew fields or infinite-dimensional representations, and does not settle whether all hyperbolic groups are sofic.

Theorem 1.1: there is a torsion-free word-hyperbolic group GG, the fundamental group of a finite Euclidean triangle complex, that is not residually finite; one member of a fixed finite family of nontrivial elements lies in the finite residual, without identifying which. Corollary 1.2: every finite-dimensional representation of GG over every commutative field kills the finite residual, so GG is linear over no field. With Kapovich-Wise this gives a nontrivial hyperbolic group with no nontrivial finite quotient and a hyperbolic group that is not virtually torsion-free (curator's reading of the paper's stated consequences). It says nothing about skew fields or infinite-dimensional representations, and does not settle whether all hyperbolic groups are sofic.

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Are all word-hyperbolic groups residually finite? — Mathematical Frontier Network