Geometric topology (object)

In mathematics, the geometric topology is a topology one can put on the set H of hyperbolic 3-manifolds of finite volume.

Convergence in this topology is a crucial ingredient of hyperbolic Dehn surgery, a fundamental tool in the theory of hyperbolic 3-manifolds.

Definition

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The following is a definition due to Troels Jorgensen:

A sequence   in H converges to M in H if there are
  • a sequence of positive real numbers   converging to 0, and
  • a sequence of  -bi-Lipschitz diffeomorphisms  
where the domains and ranges of the maps are the  -thick parts of either the  's or M.

Alternate definition

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There is an alternate definition due to Mikhail Gromov. Gromov's topology utilizes the Gromov-Hausdorff metric and is defined on pointed hyperbolic 3-manifolds. One essentially considers better and better bi-Lipschitz homeomorphisms on larger and larger balls. This results in the same notion of convergence as above as the thick part is always connected; thus, a large ball will eventually encompass all of the thick part.

On framed manifolds

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As a further refinement, Gromov's metric can also be defined on framed hyperbolic 3-manifolds. This gives nothing new but this space can be explicitly identified with torsion-free Kleinian groups with the Chabauty topology.

See also

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References

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