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Remarks on smooth manifolds + v 0.17
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Signed-off-by: Marcello Seri <[email protected]>
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mseri committed Nov 17, 2021
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5 changes: 4 additions & 1 deletion 1-manifolds.tex
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Expand Up @@ -260,7 +260,8 @@ \section{Differentiable manifolds}
\end{exercise}

\begin{definition}\label{def:diffstr}
\marginnote{The union of all atlases in a differentiable structure is the \emph{unique} \emph{maximal} atlas in the equivalence class. There is a one-to-one correspondence between differentiable structures and maximal differentiable atlases: for convenience and to lighten the notation, from now on, we will always regard a differentiable structure as a differentiable maximal atlas without further comments.}
\marginnote{The union of all atlases in a differentiable structure is the \emph{unique} \emph{maximal} atlas in the equivalence class.
There is a one-to-one correspondence between differentiable structures and maximal differentiable atlases \cite[Proposition 1.17]{book:lee}: for convenience and to lighten the notation, from now on, we will always regard a differentiable structure as a differentiable maximal atlas without further comments.}
A \emph{differentiable structure}, or more precisely a \emph{smooth structure}, on a topological manifold is an equivalence class of smooth atlases.
\end{definition}

Expand All @@ -274,6 +275,8 @@ \section{Differentiable manifolds}
\end{definition}

In colloquial language, a differentiable manifold is just a space covered by charts with differentiable transition maps.
Note that not all topological manifolds can be made into smooth manifolds, but counterexamples are hard to construct and you need at least to go to dimension 4.
A nice and super compact explanation with the relevant reference is in \cite{SE2691140}.

\begin{notation}
Whenever possible we will omit the differentiable structure $\cA$ from the notation and just write $M$.
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10 changes: 9 additions & 1 deletion aom.bib
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Expand Up @@ -197,7 +197,15 @@ @misc{lectures:teufel
@misc{nlab:urysohn_metrization_theorem,
author = {{nLab authors}},
title = {{{U}}rysohn metrization theorem},
url = {http://ncatlab.org/nlab/show/Urysohn%20metrization%20theorem/10},
url = {http://ncatlab.org/nlab/show/Urysohn%20metrization%20theorem/10},
month = nov,
year = 2020
}

@MISC {SE2691140,
TITLE = {Give me an example of a topological manifold which is not a smooth manifold.},
AUTHOR = {C. Falcon},
HOWPUBLISHED = {Mathematics Stack Exchange},
NOTE = {(version: 2018-03-14)},
URL = {https://web.archive.org/web/20211117121257/https://math.stackexchange.com/questions/2691131/give-me-an-example-of-a-topological-manifold-which-is-not-a-smooth-manifold}
}
8 changes: 4 additions & 4 deletions aom.tex
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%Next block avoids bug, from http://tex.stackexchange.com/a/200725/1913
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Copyright \copyright\ \the\year\ \thanklessauthor

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