Questions tagged [smooth-manifolds]

For questions about smooth manifolds, a topological manifold with a maximal smooth atlas.

A topological manifold of dimension $n$ is a Hausdorff, second countable topological space $X$ such that each $x \in X$ has a neighbourhood homeomorphic to an open subset of $\mathbb{R}^n$.

A smooth atlas on a topological manifold $X$ is a collection of pairs $\left\lbrace(U_{\alpha}, \varphi_{\alpha})\right\rbrace_{\alpha\in A}$ where $U_{\alpha}$ is an open subset of $X$ and $\varphi_{\alpha} : U_{\alpha} \to \varphi_{\alpha}(U_{\alpha}) \subseteq \mathbb{R}^n$ is a homeomorphism such that $\bigcup\limits_{\alpha\in A}U_{\alpha} = X$.

A topological manifold with a maximal smooth atlas is called a smooth manifold.

6282 questions
0
votes
1 answer

Very Simple Manifold Question a Chart On A Smooth Manifold is Smooth

This may seem tautological but if you have a smooth manifold $M$ of dimension $n$ by definition any chart $x:M \supset U\to \mathbb{R}^n$ is also smooth, right? The reasoning is, the differentiable structure of $M$ is determined by the collection…
Bob
  • 1,462
0
votes
0 answers

Show that $F_s(x)= |x|^{s-1}x$ is not smooth for all $s>1$ and $\frac{s-1}{2} \notin \mathbb N$

I am trying to prove that Show that $F_s(x)= ||x||^{s-1}x,x\in \mathbb R^n$ is not smooth for all $s>1$. My strategy is as follows: To simplify the problem, I would only look at its partial derivative $D_1F_s(x)$ I get that $D_1F(x_1,\cdots,x_n) =…
Keith
  • 1,383
0
votes
2 answers

A question about "smoothly compatible"

We say that two charts$(U,\phi), (V,\theta)$ are smoothly compatible if $U \cap V = \emptyset$ or $ \phi \circ \theta^{-1}$ is smooth. Do we also require that $\theta \circ \phi^{-1}$ to be smooth?
Keith
  • 1,383
0
votes
1 answer

A contractible manifold is deformation retractable to a point.

How can I prove that a contractible manifold $M$ is always deformation retractable to a point $p$? This is an exercise from the book "An introduction to Manifolds" by L. Tu. Intuitively it seems that, at each stage of the homotopy, it should be…
0
votes
0 answers

Definition of a Smooth Manifold

I know that a smooth manifold is a topological manifold whose transition maps are smooth. Must the coordinate maps also be smooth? Must they be diffeomorphisms? MathWorld seems to think so, but I do not understand why it follows from the definition…
Open Season
  • 1,332
0
votes
1 answer

Coordinates on manifold and tangent space

Let $M$ be smooth manifold and $x \in M$. $\langle v_1,\dots,v_n \rangle = T_xM$ i want to find chart $(U,x)$ such $v_i = \frac{\partial }{\partial x_i}$. Ok there is some chart $(W, y)$ and we have that $v_i = \frac{\partial }{\partial x_i} =…
qwenty
  • 1,540
0
votes
1 answer

Lie derivative and commutator.

On Do Carmo's book Riemannian Geometry in the chapter $0$ we have the following theorem: Let $X,Y$ be differentiable vector fields on a differentiable manifold $M$, let $p\in M$ and let $\phi_t$ be the local flow of $X$ in a neighborhood $U$ of…
EQJ
  • 4,369
0
votes
0 answers

How does this set of symmetric matrices form a smooth manifold?

Let $n$ and $r$ be positive integers with $3 \leq r \leq n$. Let $X$ be the set of real $n \times n$ symmetric matrices $A$ such that the submatrix of each $A$ formed by columns $1,2$ and rows $3,...,r$ has rank $1$. How does $X$ form a smooth…
SorTheene
  • 169
-1
votes
1 answer

$SL_2(\mathbb{R}) \cong S^1 \times D^2$

I’m trying to prove $SL_2(\mathbb{R}) \cong S^1 \times D^2$, but I don’t know how to construct. Where $S^1$ is the circle, and $D^2$ is the disk. Using the implicit function theorem, I could prove that $SL_2(\mathbb{R})$ is $3$-dimensions…
-1
votes
1 answer

What does $S=\{t \in I : \gamma(t)=\gamma'(t) \}$ closed in $I$ by continuity mean? Why is it different from $S$ being a open set?

Slight confusion in terminology: What does $S=\{t \in I : \gamma(t)=\hat{\gamma}(t) \}$ closed in $I$ (open interval) by continuity mean? Why is it different from $S$ being a open set? $\gamma, \hat{\gamma}:J \rightarrow M$ is are integral curves on…
mavavilj
  • 7,270
-2
votes
1 answer

Is $f \circ f^{-1}=id$ a sufficient criteria/check for diffeomorphism? Or what is?

Is $f \circ f^{-1}=id$ a sufficient criteria for diffeomorphism? I recall having seen some version which had three functions in the composition. But I also think of reading that $f \circ f^{-1}=id$ implies that both $f$ and $f^{-1}$ must be smooth.…
mavavilj
  • 7,270
1 2 3
10
11