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Hyperbolicity of a finitely generated group is independent of the finite generating set
Statement
Assume the Axiom of Choice. Let be a finitely generated group. If the Cayley graph of is hyperbolic for one finite generating set, then it is hyperbolic for every finite generating set.
Facts & Assumptions
Given: AC, a finitely generated group and two finite generating sets .
Two finite generating sets of a group give bilipschitz equivalent word metrics (The identity map between the word metrics of two finite generating sets is a bilipschitz equivalence).
Hyperbolicity is a quasi-isometry invariant of geodesic spaces (Hyperbolicity is a quasi-isometry invariant of geodesic spaces).
AC is used in [L2] through its Morse and controlled-inverse suppliers (The Axiom of Choice).
Proof
By [L1], the identity map on the vertex sets is bilipschitz for the two word metrics. Extend it over each edge of by a chosen shortest -path for that edge label, and conversely for -edges. Because the generating sets are finite, these paths can be fixed by finitely many choices. The resulting maps are quasi-isometries of the geometric Cayley graphs: every point is within of a vertex, and the vertex metrics have the bilipschitz bounds from [L1].
By [L2], under [A1] hyperbolicity transfers from one geometric Cayley graph to the other. Since were arbitrary finite generating sets, the definition does not depend on the set.
Depends on
Used by
Nothing in the library uses this result yet.
Dependency tree · two levels
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Sources
- Clara Löh, Geometric Group Theory, Section 6.3 (standard reference, not scraped)