{Arnold Dynamical System I, 1992} f diffeomorphism => derivative of f isomorphism












0












$begingroup$


Let $f$ be a diffeomorphism of $M$ onto $N$ (both $M$,$N$ are smooth manifold). Prove that the mapping $f_{*x}$ is a vector-space isomorphism
between $T_xM$ and $T_xN$.





Here is a proof:



Let $x=f^{-1}(y) in M,, yin N$ and $hin M, kin N$ and I denote $U=f_{*x}$ and $V=f^{-1}_{x*}$. We know that $U,V$ are linear maps.



We have:
$$
f(x+h)=f(x)+Uh+o(|h|)
$$

$$
f^{-1}(y+k)=f^{-1}(y)+Vk+o(|k|)
$$



Then
$$
y+k = f(f^{-1}(y)+Vk+o(|k|))=y+U(Vk+o(|k|)) +o(|Vk+o(|k|)|)
$$

which yields
$$
k=UVk
$$

for every $k$ so $U$ is invertible and $U^{-1}=V$.










share|cite|improve this question









$endgroup$












  • $begingroup$
    You could use the chain rule and prove the theorem in one line.
    $endgroup$
    – Amitai Yuval
    Jan 14 at 9:14










  • $begingroup$
    Oh yeah indeed !
    $endgroup$
    – Smilia
    Jan 14 at 9:36










  • $begingroup$
    Your operations only make sense if the manifolds are affine spaces. That could be accomplished locally by considering charts of the manifolds. On curved space in general you can not simply add a tangent vector to a point.
    $endgroup$
    – LutzL
    Jan 14 at 9:49
















0












$begingroup$


Let $f$ be a diffeomorphism of $M$ onto $N$ (both $M$,$N$ are smooth manifold). Prove that the mapping $f_{*x}$ is a vector-space isomorphism
between $T_xM$ and $T_xN$.





Here is a proof:



Let $x=f^{-1}(y) in M,, yin N$ and $hin M, kin N$ and I denote $U=f_{*x}$ and $V=f^{-1}_{x*}$. We know that $U,V$ are linear maps.



We have:
$$
f(x+h)=f(x)+Uh+o(|h|)
$$

$$
f^{-1}(y+k)=f^{-1}(y)+Vk+o(|k|)
$$



Then
$$
y+k = f(f^{-1}(y)+Vk+o(|k|))=y+U(Vk+o(|k|)) +o(|Vk+o(|k|)|)
$$

which yields
$$
k=UVk
$$

for every $k$ so $U$ is invertible and $U^{-1}=V$.










share|cite|improve this question









$endgroup$












  • $begingroup$
    You could use the chain rule and prove the theorem in one line.
    $endgroup$
    – Amitai Yuval
    Jan 14 at 9:14










  • $begingroup$
    Oh yeah indeed !
    $endgroup$
    – Smilia
    Jan 14 at 9:36










  • $begingroup$
    Your operations only make sense if the manifolds are affine spaces. That could be accomplished locally by considering charts of the manifolds. On curved space in general you can not simply add a tangent vector to a point.
    $endgroup$
    – LutzL
    Jan 14 at 9:49














0












0








0





$begingroup$


Let $f$ be a diffeomorphism of $M$ onto $N$ (both $M$,$N$ are smooth manifold). Prove that the mapping $f_{*x}$ is a vector-space isomorphism
between $T_xM$ and $T_xN$.





Here is a proof:



Let $x=f^{-1}(y) in M,, yin N$ and $hin M, kin N$ and I denote $U=f_{*x}$ and $V=f^{-1}_{x*}$. We know that $U,V$ are linear maps.



We have:
$$
f(x+h)=f(x)+Uh+o(|h|)
$$

$$
f^{-1}(y+k)=f^{-1}(y)+Vk+o(|k|)
$$



Then
$$
y+k = f(f^{-1}(y)+Vk+o(|k|))=y+U(Vk+o(|k|)) +o(|Vk+o(|k|)|)
$$

which yields
$$
k=UVk
$$

for every $k$ so $U$ is invertible and $U^{-1}=V$.










share|cite|improve this question









$endgroup$




Let $f$ be a diffeomorphism of $M$ onto $N$ (both $M$,$N$ are smooth manifold). Prove that the mapping $f_{*x}$ is a vector-space isomorphism
between $T_xM$ and $T_xN$.





Here is a proof:



Let $x=f^{-1}(y) in M,, yin N$ and $hin M, kin N$ and I denote $U=f_{*x}$ and $V=f^{-1}_{x*}$. We know that $U,V$ are linear maps.



We have:
$$
f(x+h)=f(x)+Uh+o(|h|)
$$

$$
f^{-1}(y+k)=f^{-1}(y)+Vk+o(|k|)
$$



Then
$$
y+k = f(f^{-1}(y)+Vk+o(|k|))=y+U(Vk+o(|k|)) +o(|Vk+o(|k|)|)
$$

which yields
$$
k=UVk
$$

for every $k$ so $U$ is invertible and $U^{-1}=V$.







ordinary-differential-equations derivatives proof-verification differential-geometry vector-spaces






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 14 at 8:55









SmiliaSmilia

667617




667617












  • $begingroup$
    You could use the chain rule and prove the theorem in one line.
    $endgroup$
    – Amitai Yuval
    Jan 14 at 9:14










  • $begingroup$
    Oh yeah indeed !
    $endgroup$
    – Smilia
    Jan 14 at 9:36










  • $begingroup$
    Your operations only make sense if the manifolds are affine spaces. That could be accomplished locally by considering charts of the manifolds. On curved space in general you can not simply add a tangent vector to a point.
    $endgroup$
    – LutzL
    Jan 14 at 9:49


















  • $begingroup$
    You could use the chain rule and prove the theorem in one line.
    $endgroup$
    – Amitai Yuval
    Jan 14 at 9:14










  • $begingroup$
    Oh yeah indeed !
    $endgroup$
    – Smilia
    Jan 14 at 9:36










  • $begingroup$
    Your operations only make sense if the manifolds are affine spaces. That could be accomplished locally by considering charts of the manifolds. On curved space in general you can not simply add a tangent vector to a point.
    $endgroup$
    – LutzL
    Jan 14 at 9:49
















$begingroup$
You could use the chain rule and prove the theorem in one line.
$endgroup$
– Amitai Yuval
Jan 14 at 9:14




$begingroup$
You could use the chain rule and prove the theorem in one line.
$endgroup$
– Amitai Yuval
Jan 14 at 9:14












$begingroup$
Oh yeah indeed !
$endgroup$
– Smilia
Jan 14 at 9:36




$begingroup$
Oh yeah indeed !
$endgroup$
– Smilia
Jan 14 at 9:36












$begingroup$
Your operations only make sense if the manifolds are affine spaces. That could be accomplished locally by considering charts of the manifolds. On curved space in general you can not simply add a tangent vector to a point.
$endgroup$
– LutzL
Jan 14 at 9:49




$begingroup$
Your operations only make sense if the manifolds are affine spaces. That could be accomplished locally by considering charts of the manifolds. On curved space in general you can not simply add a tangent vector to a point.
$endgroup$
– LutzL
Jan 14 at 9:49










1 Answer
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$begingroup$

Denote by $g=f^{-1}$ we have using the chain rule,



$$
d(gcirc f)[x](h) = dg[f(x)](df[x](h))
$$

which gives
$$
h = V(Uh)
$$

hence $U^{-1}=V$.






share|cite|improve this answer









$endgroup$













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    $begingroup$

    Denote by $g=f^{-1}$ we have using the chain rule,



    $$
    d(gcirc f)[x](h) = dg[f(x)](df[x](h))
    $$

    which gives
    $$
    h = V(Uh)
    $$

    hence $U^{-1}=V$.






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      Denote by $g=f^{-1}$ we have using the chain rule,



      $$
      d(gcirc f)[x](h) = dg[f(x)](df[x](h))
      $$

      which gives
      $$
      h = V(Uh)
      $$

      hence $U^{-1}=V$.






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        Denote by $g=f^{-1}$ we have using the chain rule,



        $$
        d(gcirc f)[x](h) = dg[f(x)](df[x](h))
        $$

        which gives
        $$
        h = V(Uh)
        $$

        hence $U^{-1}=V$.






        share|cite|improve this answer









        $endgroup$



        Denote by $g=f^{-1}$ we have using the chain rule,



        $$
        d(gcirc f)[x](h) = dg[f(x)](df[x](h))
        $$

        which gives
        $$
        h = V(Uh)
        $$

        hence $U^{-1}=V$.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 14 at 9:38









        SmiliaSmilia

        667617




        667617






























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