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6 votes
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Stable norm on hyperbolic surfaces

For a hyperbolic surface $S$ and a homology class $h\in H_1(S)$ its stable norm is defined as $\lim_{n\to\infty}\frac{1}{n}l(nh)$, where $l(nh)$ means the minimal length among all closed geodesics rep …
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7 votes

Can bilipschitz models of hyperbolic 3-manifolds be made effective?

See Bowditch: link text Systems of bands in hyperbolic 3-manifolds with an approach to the Brock-Canary-Minsky Theorem (though not through their model manifold) that is, in principle, effective. Thou …
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3 votes

What does it mean exactly for a pair of $S^0$'s to be unlinked on a knot $K$?

Think of $S^1$ as the ideal boundary of the hyperbolic plane, then every embedded $S^0\subset S^1$ determines a unique geodesic in the hyperbolic plane. The linking number of two embedded $S^0$s is de …
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4 votes
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What is a half cusp in hyperbolic geometry?

This means that the boundary is geodesic with cusps in the marked points. The easiest example is a disk with 3 marked points on its boundary. In this case the hyperbolic metric is given by identifica …
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4 votes
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Mostow rigidity for complex hyperbolic manifolds

The general statement of Mostow-Prasad rigidity cited from http://repository.ias.ac.in/36364/1/36364.pdf is as follows. Let $G$ (resp. $G^\prime$) be a semi-simple analytic group and $\Gamma$ (resp. …
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2 votes

Comparing the areas of polygons via equidecomposability in the hyperbolic plane

A proof is given in Example 8.10. of https://www.amazon.de/-/en/Johan-L-Dupont/dp/9810245084 . It is however not at all the elementary proof that you seem to be after. There is an exact sequence $$H_1 …
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15 votes
Accepted

Failure of Mostow rigidity in dimension 2

ad (i): First consider a Dehn twist at some simple, closed curve in a closed hyperbolic surface. It is obviously a quasi-isometry (as any smooth map between closed surfaces) but not an isometry. Th …
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6 votes

Intuition for Zagier's theorem for $\zeta_K(2)$

Too long for a comment and not sure whether this counts as a big picture, but anyway: There is a general formula for the covolume of S-arithmetic lattices in symmetric spaces, you find it in Prasad's …
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4 votes
2 answers
296 views

Quadratic cusp shape

Which hyperbolic $3$-manifolds are known to have quadratic cusp shape? Explanations: Cusps of hyperbolic $3$-manifolds are products torus x interval. They lift to horoballs in hyperbolic $3$-space, wh …
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1 vote

Dilogarithm, tetrahedrons, and hyperbolic space

In fact this follows from Stokes' theorem. Consider the 4-simplex $\sigma$ with vertices ABCDE. Since the volume form $\omega$ is closed we have $$\int_{\partial\sigma}\omega=\int_{\sigma} d\omega=0.$ …
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1 vote
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Build a Fuchsian group starting from punctures on a disk

This is a very special case of the Fock-Goncharov construction. Divide your ideal n-gon into n-2 ideal triangles. Given one cross ratio associated to each edge (i.e., to the 4 ideal vertices of the …
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3 votes
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Conformal boundary and cusp of figure-8 complement

The group of parabolic isometries fixing a point at infinity is isomorphic to ${\mathbb C}$. (Because it acts simply transitively on a horosphere $H$.) The discrete group $\Gamma$ intersects this stab …
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7 votes
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Reconciling Sullivan's theorem with the hyperbolic structure of the Figure–8 knot complement

The statement is only true if you restrict to geometrically finite hyperbolic metrics (possibly of infinite volume) and ignore parabolic elements, which basically means that you ignore the boundary …
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8 votes
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Induced homeomorphism from a quasi-isometry between hyperbolic spaces

Properness is already needed to have a well-defined boundary at infinity, i.e., with a topology not depending on the chosen base point. This is Proposition III.3.7 in Bridson-Haefliger, which builds o …
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13 votes
1 answer
1k views

Representation varieties of 3-manifold groups in $\mathrm{SL}(n,\mathbb{C})$

I am looking at the variety of representations of the fundamental group of a hyperbolic 3-manifold into $\mathrm{SL}(n,\mathbb{C})$: $$\mathrm{Hom}(\pi_1(M), \mathrm{SL}(n,{\mathbb C}))$$ It is known …
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