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.

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Why does the injectivity of the differential implies the injectivity of the derivative(Jacobian)?

I'm reading Warner. "Foundations of Differentiable Manifolds and Lie Groups." In the proof of corollary (a) in page 24, which I will present below, the book proves that the differential $df$ of the function $f: U \to \mathbb R^d$, where $U$ is open…
zxcv
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Can the surface of a 3-dimension cube be diffeomorphic to a 3-dimension sphere?

We all know the surface of a cube homeomorphic to a sphere $S^3$ by retraction, but I'm confused that whether the surface of a cube can be diffeomorphic to $S^3$.
user622044
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Injective function and compact set

Let $f:M\to N$ be a differentiable function between smooth manifolds. Let $K\subset M$ be a compact set and $f$ is injective on $K$. Also $Df$ is an isomorphism on $K$. Show that there exists an open set $U$ containing $K$ such that $f$ is injective…
bob
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Example of two different smooth structure on a manifold.

Let $M$ a manifold. Two atlas $A_1=\{(U_i,\varphi_i)\}$ and $A_2=\{(V_i,\psi_i)\}$. They define the same smooth structure if whenever $f$ is smooth wrt $A_1$ then it will be smooth wrt $A_2$. For example $$A_1=\{(\mathbb R^n,id_{\mathbb…
Peter
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Verification of a manifold

Prove that $$\{(a,b,c) \in \mathbb{C}^3|a^5+b^3+c^2=0,|a|^2+|b|^2+|c|^2=1\}$$ is a 3 dimensional compact smooth (real) manifold and calculate its fundamental group $\pi_1$. I wonder if there's a way to check without invoking(and with brute force)…
Focus
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Integration of $k$ forms

Let $M$ be an n dimensional manifold and $\omega$ a $k
EQJ
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Curves inside the Grassmanian.

Let $G_{n,k}$ be the grassmanian the manifold of the $k$-dimensional vector space contain in $\mathbb{R}^n$. Prove that there exists a differentiable aplication $W:(a,b)\rightarrow G_{n,k}$ iff there exist $Y_1,\dots Y_k:(a,b)\rightarrow…
EQJ
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Geometry on manifolds - Adapted coordinate chart for a curve

Let $M$ be a smooth manifold and $\gamma:I\to M$ a smooth curve on $M$. How can I construct a local chart $(U,\psi)$ such that $U\cap \gamma(I)\ne \emptyset$ and $\gamma(t)\equiv(\gamma^1(t),0,\ldots,0)$ for all $t$?
FUUNK1000
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Change $C^1$-embedding to a homotopic $C^\infty$-embedding

I have a $C^1$-embedding of $\mathbb{S}^1$ into some smooth manifold. How do i prove, that there exists a homotopic $C^\infty$-embedding of $\mathbb{S}^1$? Is it easier for some $r\geq 3$ to prove, that a homotopic $C^r$-embedding embedding exists?…
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Making a path in a manifold differentiable

I have a closed path in a smooth compact Manifold $C \subset M$, that consists of straight pieces, so $C = \alpha \circ \beta \circ ... \circ \delta$, where $\circ$ is the concatenation, and $\alpha = tx + (1-t)y$ , $\beta = ty+(1-t)z ,...$ for…
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Why the map $v_a \mapsto D_v|_a$ is injective from $\mathbb{R}_a^n$ onto $T_a \mathbb{R}^n$

Notations are from John M.Lee's book Introduction to smooth manifolds. $\mathbb{R}_a^n=\{a\}\times \mathbb{R}^n=\{(a,v):v \in\mathbb{R}^n\}$ $D_v|a:C^\infty(\mathbb{R}^n\to\mathbb{R})$,$f\mapsto \frac{d}{dt}|_{t=0}f(a+tv)$. Since the directional…
Brooks
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Is being an image of an immersion a local propery?

Suppose I have a manifold $M$ (without boundary) and a subset $S$ such that it is locally an image of an immersion. Namely, for any $s\in S$ there exists an open set $U_s \subset M$ with $s \in U_s$, a manifold $N_s$ and an immersion $i_s: N_s \to…
Max
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If $M$ can be immersed in $\mathbb{R}^k\times(S^1)^l$ with codimension $1$, can it be immersed in $\mathbb{R}^{k+l}$ with codimension $1$?

Suppose a smooth manifold $M^n$ can be immersed in $E = \mathbb{R}^k \times \mathbb{S}^1 \times \cdots \times \mathbb{S}^1$ with codimension $1$, where there are, say, $l$ factors $\mathbb{S}^1$. Is it true that $M$ can also be immersed in…
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Trying to calculate the degree of a map

I am trying to calculate the degree of a map $f:\mathbb CP^1\rightarrow \mathbb CP^1$ such that $f([x:y])=[x^8+y^8:x^8-y^8]$. The $[x:y]$ are homogenous coordinates. I have been trying to claculate this for long, but all my proofs seem incorrect -…
MasterJ
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How can I see that the product smooth manifold structure is a maximal atlas?

I want to explicitly specify a maximal smooth atlas on a $\mathbb{T}^2$. I am following John Lee - introduction to smooth manifolds. He writes that the product smooth manifold structure defines a smooth structure on $\mathbb{T}^n = \mathbb{S}^1…
Mikkel Rev
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