Understanding Embedded submanifolds and immersions












0












$begingroup$


I am trying to understand the concept of embedded submanifolds and have the following understanding:



Suppose we have a smooth manifold $M$ and $N$ of dimensions $m$ and $n$ such that $mgt n$ .Let $Fcolon Nto M$ be a smooth map and a topological embedding onto its image $F(N)$ under subspace topology that $F(N)$ inherits from $M$. So, there is a smooth structure on $F(N)$ such that $Fcolon N to F(N)$ is a diffeomorphism (the smooth coordinate maps are just maps of the form $fcirc F^{-1}$, where $f$ is a smooth coordinate map for $N$). Therefore, it gives us a smooth manifold $F(N)$ of dimension similar as $N$ which sits inside $M$.



Now, the definition of embedded submanifolds as given in the text of boothby is:




image of a topological embedding+immersion is an embedded submanifold




My problem is:



If just taking $Fcolon N to F(N)$ as a topological embedding gives $F(N)$ diffeomorphic to $N$. So, it gives a smooth manifold $F(N)$ with same dimension as $N$, why do we even need to consider immersions?



Thanks in advance










share|cite|improve this question











$endgroup$












  • $begingroup$
    What is the definition of topological embedding here?
    $endgroup$
    – Anubhav Mukherjee
    Jan 10 at 18:48










  • $begingroup$
    @Anubhav Mukherjee:it is a homeomorphism from N to f(N),where f(N) has subspace topology
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 18:50
















0












$begingroup$


I am trying to understand the concept of embedded submanifolds and have the following understanding:



Suppose we have a smooth manifold $M$ and $N$ of dimensions $m$ and $n$ such that $mgt n$ .Let $Fcolon Nto M$ be a smooth map and a topological embedding onto its image $F(N)$ under subspace topology that $F(N)$ inherits from $M$. So, there is a smooth structure on $F(N)$ such that $Fcolon N to F(N)$ is a diffeomorphism (the smooth coordinate maps are just maps of the form $fcirc F^{-1}$, where $f$ is a smooth coordinate map for $N$). Therefore, it gives us a smooth manifold $F(N)$ of dimension similar as $N$ which sits inside $M$.



Now, the definition of embedded submanifolds as given in the text of boothby is:




image of a topological embedding+immersion is an embedded submanifold




My problem is:



If just taking $Fcolon N to F(N)$ as a topological embedding gives $F(N)$ diffeomorphic to $N$. So, it gives a smooth manifold $F(N)$ with same dimension as $N$, why do we even need to consider immersions?



Thanks in advance










share|cite|improve this question











$endgroup$












  • $begingroup$
    What is the definition of topological embedding here?
    $endgroup$
    – Anubhav Mukherjee
    Jan 10 at 18:48










  • $begingroup$
    @Anubhav Mukherjee:it is a homeomorphism from N to f(N),where f(N) has subspace topology
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 18:50














0












0








0





$begingroup$


I am trying to understand the concept of embedded submanifolds and have the following understanding:



Suppose we have a smooth manifold $M$ and $N$ of dimensions $m$ and $n$ such that $mgt n$ .Let $Fcolon Nto M$ be a smooth map and a topological embedding onto its image $F(N)$ under subspace topology that $F(N)$ inherits from $M$. So, there is a smooth structure on $F(N)$ such that $Fcolon N to F(N)$ is a diffeomorphism (the smooth coordinate maps are just maps of the form $fcirc F^{-1}$, where $f$ is a smooth coordinate map for $N$). Therefore, it gives us a smooth manifold $F(N)$ of dimension similar as $N$ which sits inside $M$.



Now, the definition of embedded submanifolds as given in the text of boothby is:




image of a topological embedding+immersion is an embedded submanifold




My problem is:



If just taking $Fcolon N to F(N)$ as a topological embedding gives $F(N)$ diffeomorphic to $N$. So, it gives a smooth manifold $F(N)$ with same dimension as $N$, why do we even need to consider immersions?



Thanks in advance










share|cite|improve this question











$endgroup$




I am trying to understand the concept of embedded submanifolds and have the following understanding:



Suppose we have a smooth manifold $M$ and $N$ of dimensions $m$ and $n$ such that $mgt n$ .Let $Fcolon Nto M$ be a smooth map and a topological embedding onto its image $F(N)$ under subspace topology that $F(N)$ inherits from $M$. So, there is a smooth structure on $F(N)$ such that $Fcolon N to F(N)$ is a diffeomorphism (the smooth coordinate maps are just maps of the form $fcirc F^{-1}$, where $f$ is a smooth coordinate map for $N$). Therefore, it gives us a smooth manifold $F(N)$ of dimension similar as $N$ which sits inside $M$.



Now, the definition of embedded submanifolds as given in the text of boothby is:




image of a topological embedding+immersion is an embedded submanifold




My problem is:



If just taking $Fcolon N to F(N)$ as a topological embedding gives $F(N)$ diffeomorphic to $N$. So, it gives a smooth manifold $F(N)$ with same dimension as $N$, why do we even need to consider immersions?



Thanks in advance







differential-geometry manifolds differential-topology smooth-manifolds






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 10 at 18:44









Christoph

12k1642




12k1642










asked Jan 10 at 18:39









Abhishek ShrivastavaAbhishek Shrivastava

414413




414413












  • $begingroup$
    What is the definition of topological embedding here?
    $endgroup$
    – Anubhav Mukherjee
    Jan 10 at 18:48










  • $begingroup$
    @Anubhav Mukherjee:it is a homeomorphism from N to f(N),where f(N) has subspace topology
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 18:50


















  • $begingroup$
    What is the definition of topological embedding here?
    $endgroup$
    – Anubhav Mukherjee
    Jan 10 at 18:48










  • $begingroup$
    @Anubhav Mukherjee:it is a homeomorphism from N to f(N),where f(N) has subspace topology
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 18:50
















$begingroup$
What is the definition of topological embedding here?
$endgroup$
– Anubhav Mukherjee
Jan 10 at 18:48




$begingroup$
What is the definition of topological embedding here?
$endgroup$
– Anubhav Mukherjee
Jan 10 at 18:48












$begingroup$
@Anubhav Mukherjee:it is a homeomorphism from N to f(N),where f(N) has subspace topology
$endgroup$
– Abhishek Shrivastava
Jan 10 at 18:50




$begingroup$
@Anubhav Mukherjee:it is a homeomorphism from N to f(N),where f(N) has subspace topology
$endgroup$
– Abhishek Shrivastava
Jan 10 at 18:50










1 Answer
1






active

oldest

votes


















1












$begingroup$

Let $N=Bbb R$ and $M=Bbb R^2$. The map $Fcolon Nto M$, $xmapsto (x^3,0)$ is a topological embedding of $Bbb R$ into $Bbb R^2$. However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$. (The two smooth structures on $F(N)$ yield diffeomorphic manifolds, but are not equivalent.) To avoid this, you want $F$ to be an immersion, so that both smooth structures (the one pushed forward via $F$ and the one inherited from $M$) are the same.





From $M$ the subspace $Bbb Rtimes 0$ inherits a smooth structure with atlas defined by the global chart $(x,0)mapsto x$. Pushed forward via $F$, we get a smooth structure on $Bbb Rtimes 0$ with atlas defined by the global chart $(x,0)mapsto x^{1/3}$. Now check that with respect to these two atlases the identity map $Bbb Rtimes 0 to Bbb Rtimes 0$ is not a diffeomorphism, so the two smooth structures are different. They still define diffeomorphic manifolds, since $(x,0)mapsto (x^3,0)$ is a diffeomorphism with respect to these two atlases.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    :thanks for the answer.could you elaborate:"However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$"
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:05












  • $begingroup$
    I added some details, does this help?
    $endgroup$
    – Christoph
    Jan 10 at 19:14










  • $begingroup$
    :understood....thanks a lot
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:16










  • $begingroup$
    :just to ask one more thing:
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:16










  • $begingroup$
    :just to ask one more thing:as you told,i think i can have f(N) as a differentiable manifold just by considering a topological embedding as it gives a diffeomorphism but the differential structure so obtained on f(N) might not be related at all to the differential structure of manifold M in which f(N) sits.to avoid this,we define them as immersion which identifies tangent space at point p of $pmb N$ with a n dimensional subspace of tangent space at f(p) of $pmb M$"is this correct??
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:25











Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














draft saved

draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3069022%2funderstanding-embedded-submanifolds-and-immersions%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









1












$begingroup$

Let $N=Bbb R$ and $M=Bbb R^2$. The map $Fcolon Nto M$, $xmapsto (x^3,0)$ is a topological embedding of $Bbb R$ into $Bbb R^2$. However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$. (The two smooth structures on $F(N)$ yield diffeomorphic manifolds, but are not equivalent.) To avoid this, you want $F$ to be an immersion, so that both smooth structures (the one pushed forward via $F$ and the one inherited from $M$) are the same.





From $M$ the subspace $Bbb Rtimes 0$ inherits a smooth structure with atlas defined by the global chart $(x,0)mapsto x$. Pushed forward via $F$, we get a smooth structure on $Bbb Rtimes 0$ with atlas defined by the global chart $(x,0)mapsto x^{1/3}$. Now check that with respect to these two atlases the identity map $Bbb Rtimes 0 to Bbb Rtimes 0$ is not a diffeomorphism, so the two smooth structures are different. They still define diffeomorphic manifolds, since $(x,0)mapsto (x^3,0)$ is a diffeomorphism with respect to these two atlases.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    :thanks for the answer.could you elaborate:"However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$"
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:05












  • $begingroup$
    I added some details, does this help?
    $endgroup$
    – Christoph
    Jan 10 at 19:14










  • $begingroup$
    :understood....thanks a lot
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:16










  • $begingroup$
    :just to ask one more thing:
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:16










  • $begingroup$
    :just to ask one more thing:as you told,i think i can have f(N) as a differentiable manifold just by considering a topological embedding as it gives a diffeomorphism but the differential structure so obtained on f(N) might not be related at all to the differential structure of manifold M in which f(N) sits.to avoid this,we define them as immersion which identifies tangent space at point p of $pmb N$ with a n dimensional subspace of tangent space at f(p) of $pmb M$"is this correct??
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:25
















1












$begingroup$

Let $N=Bbb R$ and $M=Bbb R^2$. The map $Fcolon Nto M$, $xmapsto (x^3,0)$ is a topological embedding of $Bbb R$ into $Bbb R^2$. However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$. (The two smooth structures on $F(N)$ yield diffeomorphic manifolds, but are not equivalent.) To avoid this, you want $F$ to be an immersion, so that both smooth structures (the one pushed forward via $F$ and the one inherited from $M$) are the same.





From $M$ the subspace $Bbb Rtimes 0$ inherits a smooth structure with atlas defined by the global chart $(x,0)mapsto x$. Pushed forward via $F$, we get a smooth structure on $Bbb Rtimes 0$ with atlas defined by the global chart $(x,0)mapsto x^{1/3}$. Now check that with respect to these two atlases the identity map $Bbb Rtimes 0 to Bbb Rtimes 0$ is not a diffeomorphism, so the two smooth structures are different. They still define diffeomorphic manifolds, since $(x,0)mapsto (x^3,0)$ is a diffeomorphism with respect to these two atlases.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    :thanks for the answer.could you elaborate:"However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$"
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:05












  • $begingroup$
    I added some details, does this help?
    $endgroup$
    – Christoph
    Jan 10 at 19:14










  • $begingroup$
    :understood....thanks a lot
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:16










  • $begingroup$
    :just to ask one more thing:
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:16










  • $begingroup$
    :just to ask one more thing:as you told,i think i can have f(N) as a differentiable manifold just by considering a topological embedding as it gives a diffeomorphism but the differential structure so obtained on f(N) might not be related at all to the differential structure of manifold M in which f(N) sits.to avoid this,we define them as immersion which identifies tangent space at point p of $pmb N$ with a n dimensional subspace of tangent space at f(p) of $pmb M$"is this correct??
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:25














1












1








1





$begingroup$

Let $N=Bbb R$ and $M=Bbb R^2$. The map $Fcolon Nto M$, $xmapsto (x^3,0)$ is a topological embedding of $Bbb R$ into $Bbb R^2$. However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$. (The two smooth structures on $F(N)$ yield diffeomorphic manifolds, but are not equivalent.) To avoid this, you want $F$ to be an immersion, so that both smooth structures (the one pushed forward via $F$ and the one inherited from $M$) are the same.





From $M$ the subspace $Bbb Rtimes 0$ inherits a smooth structure with atlas defined by the global chart $(x,0)mapsto x$. Pushed forward via $F$, we get a smooth structure on $Bbb Rtimes 0$ with atlas defined by the global chart $(x,0)mapsto x^{1/3}$. Now check that with respect to these two atlases the identity map $Bbb Rtimes 0 to Bbb Rtimes 0$ is not a diffeomorphism, so the two smooth structures are different. They still define diffeomorphic manifolds, since $(x,0)mapsto (x^3,0)$ is a diffeomorphism with respect to these two atlases.






share|cite|improve this answer











$endgroup$



Let $N=Bbb R$ and $M=Bbb R^2$. The map $Fcolon Nto M$, $xmapsto (x^3,0)$ is a topological embedding of $Bbb R$ into $Bbb R^2$. However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$. (The two smooth structures on $F(N)$ yield diffeomorphic manifolds, but are not equivalent.) To avoid this, you want $F$ to be an immersion, so that both smooth structures (the one pushed forward via $F$ and the one inherited from $M$) are the same.





From $M$ the subspace $Bbb Rtimes 0$ inherits a smooth structure with atlas defined by the global chart $(x,0)mapsto x$. Pushed forward via $F$, we get a smooth structure on $Bbb Rtimes 0$ with atlas defined by the global chart $(x,0)mapsto x^{1/3}$. Now check that with respect to these two atlases the identity map $Bbb Rtimes 0 to Bbb Rtimes 0$ is not a diffeomorphism, so the two smooth structures are different. They still define diffeomorphic manifolds, since $(x,0)mapsto (x^3,0)$ is a diffeomorphism with respect to these two atlases.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Jan 10 at 19:13

























answered Jan 10 at 19:01









ChristophChristoph

12k1642




12k1642












  • $begingroup$
    :thanks for the answer.could you elaborate:"However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$"
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:05












  • $begingroup$
    I added some details, does this help?
    $endgroup$
    – Christoph
    Jan 10 at 19:14










  • $begingroup$
    :understood....thanks a lot
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:16










  • $begingroup$
    :just to ask one more thing:
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:16










  • $begingroup$
    :just to ask one more thing:as you told,i think i can have f(N) as a differentiable manifold just by considering a topological embedding as it gives a diffeomorphism but the differential structure so obtained on f(N) might not be related at all to the differential structure of manifold M in which f(N) sits.to avoid this,we define them as immersion which identifies tangent space at point p of $pmb N$ with a n dimensional subspace of tangent space at f(p) of $pmb M$"is this correct??
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:25


















  • $begingroup$
    :thanks for the answer.could you elaborate:"However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$"
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:05












  • $begingroup$
    I added some details, does this help?
    $endgroup$
    – Christoph
    Jan 10 at 19:14










  • $begingroup$
    :understood....thanks a lot
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:16










  • $begingroup$
    :just to ask one more thing:
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:16










  • $begingroup$
    :just to ask one more thing:as you told,i think i can have f(N) as a differentiable manifold just by considering a topological embedding as it gives a diffeomorphism but the differential structure so obtained on f(N) might not be related at all to the differential structure of manifold M in which f(N) sits.to avoid this,we define them as immersion which identifies tangent space at point p of $pmb N$ with a n dimensional subspace of tangent space at f(p) of $pmb M$"is this correct??
    $endgroup$
    – Abhishek Shrivastava
    Jan 10 at 19:25
















$begingroup$
:thanks for the answer.could you elaborate:"However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$"
$endgroup$
– Abhishek Shrivastava
Jan 10 at 19:05






$begingroup$
:thanks for the answer.could you elaborate:"However, the image $F(N)=Bbb Rtimes 0subset Bbb R^2$ does not inherit the same smooth structure as a subspace of $M$ as it does by pushing forward the smooth structure from $N$"
$endgroup$
– Abhishek Shrivastava
Jan 10 at 19:05














$begingroup$
I added some details, does this help?
$endgroup$
– Christoph
Jan 10 at 19:14




$begingroup$
I added some details, does this help?
$endgroup$
– Christoph
Jan 10 at 19:14












$begingroup$
:understood....thanks a lot
$endgroup$
– Abhishek Shrivastava
Jan 10 at 19:16




$begingroup$
:understood....thanks a lot
$endgroup$
– Abhishek Shrivastava
Jan 10 at 19:16












$begingroup$
:just to ask one more thing:
$endgroup$
– Abhishek Shrivastava
Jan 10 at 19:16




$begingroup$
:just to ask one more thing:
$endgroup$
– Abhishek Shrivastava
Jan 10 at 19:16












$begingroup$
:just to ask one more thing:as you told,i think i can have f(N) as a differentiable manifold just by considering a topological embedding as it gives a diffeomorphism but the differential structure so obtained on f(N) might not be related at all to the differential structure of manifold M in which f(N) sits.to avoid this,we define them as immersion which identifies tangent space at point p of $pmb N$ with a n dimensional subspace of tangent space at f(p) of $pmb M$"is this correct??
$endgroup$
– Abhishek Shrivastava
Jan 10 at 19:25




$begingroup$
:just to ask one more thing:as you told,i think i can have f(N) as a differentiable manifold just by considering a topological embedding as it gives a diffeomorphism but the differential structure so obtained on f(N) might not be related at all to the differential structure of manifold M in which f(N) sits.to avoid this,we define them as immersion which identifies tangent space at point p of $pmb N$ with a n dimensional subspace of tangent space at f(p) of $pmb M$"is this correct??
$endgroup$
– Abhishek Shrivastava
Jan 10 at 19:25


















draft saved

draft discarded




















































Thanks for contributing an answer to Mathematics Stack Exchange!


  • Please be sure to answer the question. Provide details and share your research!

But avoid



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


Use MathJax to format equations. MathJax reference.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3069022%2funderstanding-embedded-submanifolds-and-immersions%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

MongoDB - Not Authorized To Execute Command

in spring boot 2.1 many test slices are not allowed anymore due to multiple @BootstrapWith

How to fix TextFormField cause rebuild widget in Flutter