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7 votes
Accepted

A question about embedding hyperbolic space onto pseudosphere

You should be looking at the theory of Bäcklund transformations for surfaces of Gaussian curvature $K=-1$. There is a large literature on this, and there are many examples of pseudospherical immersio …
Robert Bryant's user avatar
10 votes

Geodesics on a hyperbolic paraboloid

I was working on answering another question involving integrating the geodesic equations on a surface, and the links there lead me back to this question, which I hadn't noticed before. In case anyone …
Robert Bryant's user avatar
5 votes

Vertices of hyperbolic triangle with given angles

The simplest way I know is to use the second hyperbolic law of cosines to find the lengths of the sides of the triangle, which then reduces the problem to taking two square roots plus some rational ma …
Robert Bryant's user avatar
15 votes

Reference for the proof that Möbius transformations extend to isometries of hyperbolic 3-space

Probably, you can find a discussion of this in Thurston's notes on hyperbolic 3-manifolds, or maybe some of the expositions by his students. However, what you are asking for is actually pretty simple: …
Robert Bryant's user avatar
21 votes
Accepted

Geometry of the space of circles in the Euclidean plane

Things will simplify if you just consider the circles on the Riemann sphere $S^2 = \mathbb{C}\cup\{\infty\}$, for your space is simply the space of circles on the sphere (with the lines in $\mathbb{C} …
Robert Bryant's user avatar
1 vote
Accepted

What is the name of this geometric structure, where we identify each sphere of vision with t...

This notion of 'the sphere at infinity' is commonly encountered in hyperbolic geometries. Gromov, in particular, has used it in studying the behavior of discrete transformation groups on hyperbolic m …
Robert Bryant's user avatar
13 votes

Surfaces with non-constant negative curvature

If you just want examples for which it's not hard to figure out how the geodesics behave, here's a class of examples with negative and non-constant curvauture in the plane where the geodesics are rela …
Robert Bryant's user avatar
4 votes
Accepted

The points of half area of a triangle

I believe that the answer is that the curvature of $S$ has to vanish, i.e., the surface is locally isometric to the plane. I haven't checked all of the details, which are somewhat messy in my analysi …
Robert Bryant's user avatar
11 votes
Accepted

Riemannian submersions from complex hyperbolic space into the hyperbolic space

I don't have a complete answer, but here are a few remarks about this that you may find interesting or useful: The OP didn't specify exactly what was meant by 'complex hyperbolic space' $\mathbb{CH}^ …
Robert Bryant's user avatar
17 votes
Accepted

Geodesics on the twisted pseudosphere (Dini's surface)

To answer Joseph's questions: First, it's not impossible to integrate the geodesic flow of the hyperbolic plane in these coordinates, but the formulae I got aren't very nice, so I'm not going to type …
Robert Bryant's user avatar
5 votes

Is there an absolute geometry that underlies spherical, Euclidean and hyperbolic geometry?

I'm not sure exactly what you mean by 'absolute geometry' that unifies spherical, Euclidean, and hyperbolic geometry, but in the sense of Klein's identification of geometries with group actions, so th …
Robert Bryant's user avatar
7 votes
Accepted

Isomorphism between the hyperbolic space and the manifold of SPD matrices with constant dete...

This 'isomorphism' does not hold for $n>2$, in the sense that the 'natural' $\mathrm{SL}(n,\mathbb{R})$-invariant metric on what you are calling $\mathcal{SP}(n)$ and the constant sectional curvature …
Robert Bryant's user avatar
6 votes

Canonical immersion of the double torus

This is not really an answer, but rather a longish comment and a suggestion about how one might focus the question a bit better. First, when one asks for a 'canonical' isometric embedding into some E …
Robert Bryant's user avatar
13 votes

Isometry group of a compact hyperbolic surface

I'll just point out an answer based on somewhat different criteria than explicitly knowing features of the hyperbolic metric: As is well-known, every oriented, compact hyperbolic surface $C$ is canon …
Robert Bryant's user avatar
3 votes
Accepted

Tzitzeica surface

The answer is 'no'. Suppose that $M\subset\mathbb{E}^3$ is a smooth connected surface. If the ratio of the Gauss curvature $K$ and $p^4$ is constant (where $p(x)$ is the distance from $T_xM$ to the o …
Robert Bryant's user avatar