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Complex, contact, Riemannian, pseudo-Riemannian and Finsler geometry, relativity, gauge theory, global analysis.

5 votes
Accepted

Is the extrinsic metric and intrinsic metric equivalent if second fundamental form is bounded

No, this is not true. For $L>0$, consider two lines in $\mathbb{R}^2$: $\{(x,0) : 0 \leq x \leq L\}$ and $\{(x,2) : 0 \leq x \leq L\}$. These can be "capped" at either end with half-circles of r …
Otis Chodosh's user avatar
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5 votes

A question about Schwarzschild manifold

I'm interpreting your question in the only reasonable manner that I can think of: $M= \mathbb{R}^3\backslash \{0\}$ and $g_m = \left( 1 + \frac{m}{2r}\right)\delta$ is the "doubled" Schwarzschild. …
Otis Chodosh's user avatar
  • 7,197
2 votes

Positive scalar curvature Yamabe metrics near a zero scalar curvature Yamabe metric

A result of Fischer--Marsden (Duke "Deformations of the Scalar Curvature" 1975) says that if $(M,g)$ is scalar flat, but not Ricci flat, then the scalar curvature map $R :\{metrics\} \to \{functions\} …
Otis Chodosh's user avatar
  • 7,197
4 votes
Accepted

Minor technical question in diff geometry

The notation is potentially confusing, but the end result is correct. Essentially this claim is the relationship between the area and the energy of of a conformal map. Here is a slightly expanded pr …
Otis Chodosh's user avatar
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5 votes

Complete gradient shrinking Ricci solitons not having non-negative curvature

My comment seemed to get jumbled, so here is an expanded version: In 3-d, an ancient complete Ricci flow (so, in particular a shrinking soliton) will have non-negative sectional curvature. This follo …
Otis Chodosh's user avatar
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6 votes
Accepted

How does the inverse mean curvature flow start with minimal surface?

It isn't clear exactly what sort of initial conditions you're requiring. The difficulty with minimal initial conditions is part of the reason why it was an amazing result when Huisken--Ilmanen const …
Otis Chodosh's user avatar
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3 votes
0 answers
140 views

Cheeger--Gromoll's splitting theorem with weaker assumptions on the geodesic

Cheeger and Gromoll proved the well known splitting theorem: If $(M,g)$ is a complete manifold with $Ric\geq 0$ that contains a line, then $M$ splits isometrically as $M' \times \mathbb{R}$. He …
Otis Chodosh's user avatar
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8 votes
Accepted

A general theory for local moduli space of minimal surface?

In general, asking whether or not all Jacobi fields on a minimal surface can be "integrated" to find a nearby minimal surface is a very difficult problem. For example, see Yau's remark here (page 246) …
Otis Chodosh's user avatar
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4 votes
Accepted

Derivation of yamabe flow

The Yamabe flow is (up to a constant) the gradient flow of the Yamabe functional on the unit volume conformal class, as you expected. The comment by @Mark Peletier hints at your error: you aren't usin …
Otis Chodosh's user avatar
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2 votes
Accepted

Implicit function theorem for operator

Consider the map $F:C^{2,\alpha}\to \mathbb{R}^A \times (C^{0,\alpha}\cap Im \Pi)$ $$ F: f \mapsto \left( \left(\int u_\infty^{\frac{4}{n-2}}(f-u_\infty)\psi_a\right)_{a\in A},\Pi\left( \frac{4(n-1)}{ …
Otis Chodosh's user avatar
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3 votes
Accepted

The limit of a sequence of embedded minimal disks in $\mathbb{R}^3$

A first answer is (under much weaker hypothesis than you require) Answer 1: If $\Sigma_k$ are a sequence of minimal surfaces with $\partial\Sigma_k \subset B(0,r_k)$ with $r_k\to\infty$ and $ …
Otis Chodosh's user avatar
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5 votes
Accepted

A surface on which all regular curves have nowhere vanishing curvature

I'm going to assume that you mean the following property $S \subset \mathbb{R}^3$ has property (*) if for any regular curve $\gamma\subset S$, the curvature vector $\vec{\kappa}$ of $\gamma$ as a …
Otis Chodosh's user avatar
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2 votes
Accepted

Uniqueness of backward heat equation on closed manifold with given initial data

I'm assuming you are supposing that $f\in C^\infty(M)$ for each $t \in [0,T]$, or something along this line. I'm not sure what happens if you allow $f$ to have some singularities. Then, picking any $0 …
Otis Chodosh's user avatar
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3 votes

Bryant Soliton is asymptotically cylindrical?

One method is to repeat in dimensions $n$ Bryant's analysis in which he proves the existence and uniqueness of the so called Bryant soliton in $3$-dimensions: http://www.math.duke.edu/~bryant/3DRotSym …
Otis Chodosh's user avatar
  • 7,197
5 votes

About hypersurfaces in R^n+1 with bounded 2nd fundamental form

This is a standard fact which is often asserted in the literature. A proof is given here: http://www.ugr.es/~jmmanzano/santalo/notes/GiuseppeTinaglia-Santalo-Granada.pdf (section 1), but I don't know …
Otis Chodosh's user avatar
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