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Euclidean, hyperbolic, discrete, convex, coarse geometry, metric spaces, comparisons in Riemannian geometry, symmetric spaces.
28
votes
3
answers
2k
views
Does isometric immersion map boundary to boundary?
Let $M$ be a compact, connected, oriented, smooth Riemannian manifold with non-empty boundary. Let $f:M \to M$ be a smooth orientation preserving isometric immersion.
Is it true that $f(\partial M) \ …
10
votes
2
answers
916
views
Is there a volume-preserving diffeomorphism of the disk with prescribed singular values?
This is a cross-post. While working on a variational problem, I have reached to the following question.
Let $0<\sigma_1<\sigma_2$ satisfy $\sigma_1\sigma_2=1$, and let $D \subseteq \mathbb{R}^2$ be t …
2
votes
0
answers
68
views
Are spherical maps with low distortion locally expanding?
$\newcommand{\SO}[1]{\text{SO}(#1)}$
$\newcommand{\Hom}[1]{\text{Hom}(#1)}$
$\newcommand{\R}{\mathbb{R}}$
$\newcommand{\S}{\mathbb{S}}$
The question in a nutshell: Are the "best" spherical maps local …
25
votes
1
answer
2k
views
Is it possible for a metric on a smooth manifold to be smooth?
Are there any smooth manifolds $M$ with the following property:
There exist a realizing metric $d$ (i.e $d$ induces the topology on $M$), and $d$ is smooth on all of $M \times M$?
If not, is it po …
1
vote
1
answer
251
views
Determining the rate of spread of geodesics when the sectional curvature is zero
I have posted this question in mathSE a few weeks ago (and proposed a bounty) but so far got no response.
In the book Riemanian geometry (by do-Carmo), the following result is proved (Corollary 2.9 p …
2
votes
There is no arcwise isometry from a high dimensional manifold into a low dimensional manifold
I am completenig some details based on Anton's answer:
We prove the following theorem:
Let $X,Y$ be Riemannian manifolds, and let $f:X \to Y$ be a length preserving map. Then $df$ is an isometry alm …
9
votes
2
answers
497
views
There is no arcwise isometry from a high dimensional manifold into a low dimensional manifold
$\newcommand{\al}{\alpha}$
$\newcommand{\ga}{\gamma}$
$\newcommand{\e}{\epsilon}$
Let $X,Y$ be Riemannian manifolds, such that $\dim(X) > \dim(Y)$.
I am trying to prove the following statement (ment …
7
votes
1
answer
373
views
Are metric isometries smooth at the boundary?
Let $M,N$ be smooth Riemannian manifolds with boundary (In particular, we assume the boundaries are smooth).
Suppose we have a map $\phi:M \to N$ which satisfies the following properties:
$$(1) \, \ …
8
votes
1
answer
320
views
Does nonexpanding map between manifolds decrease volume?
(This question is a special case of a question I asked at SE, which got no answer there)
Let $M,N$ be diffeomorphic connected compact Riemannian manifolds, and let $f:M \to N$ be a surjective nonexp …
3
votes
References for metrics in matrix groups
This paper might give you some ideas on how to calculate the geodesics. It is about left invariant metrics on $GL_n(\mathbb{R})$. The geodesics are calculated using their characterization as critical …
0
votes
Accepted
Characterizing left invariant and right-$O_n$ invariant distances on $GL_n$
$\newcommand{\al}{\alpha}$
The answer is no, there are many more such metric which are not induced by a Riemannian metric.
(This answer is based on the comments above, made by user89334).
Examples:
…
2
votes
1
answer
109
views
Characterizing left invariant and right-$O_n$ invariant distances on $GL_n$
Consider the group $GL_n(\mathbb{R})$ with its standard topology.
It is not hard to show that there exists Riemannian metrics on it which are left-$GL_n$ and right-$O_n$ invariant. (In fact it's pos …
11
votes
1
answer
715
views
Strong equivalence between intrinsic and extrinsic metrics on $GL_n^+$?
$\newcommand{\til}{\tilde}$
Lately, I have become interested in comparing intrinsic and extrinsic metrics on Riemannian manifolds.
Consider $GL_n^+$ (invertible matrices , $\det >0$) as an open Riem …