Two forms related by an automorphism are in the same cohomology class?

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Let $f: M to M$ define an automorphism on the smooth manifold M.



Given a differential form $omega in Omega^k$ is it true that the de Rham cohomology class of $omega$ and $f^*omega$ are the same? That is, does $[omega]=[f^*omega]$.










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    $begingroup$
    Here's another type of example: Consider the antipodal map ($f(x)=-x$) on $S^n$ with $n$ even.
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    – Ted Shifrin
    Mar 14 at 16:29















3












$begingroup$


Let $f: M to M$ define an automorphism on the smooth manifold M.



Given a differential form $omega in Omega^k$ is it true that the de Rham cohomology class of $omega$ and $f^*omega$ are the same? That is, does $[omega]=[f^*omega]$.










share|cite|improve this question









$endgroup$







  • 1




    $begingroup$
    Here's another type of example: Consider the antipodal map ($f(x)=-x$) on $S^n$ with $n$ even.
    $endgroup$
    – Ted Shifrin
    Mar 14 at 16:29













3












3








3





$begingroup$


Let $f: M to M$ define an automorphism on the smooth manifold M.



Given a differential form $omega in Omega^k$ is it true that the de Rham cohomology class of $omega$ and $f^*omega$ are the same? That is, does $[omega]=[f^*omega]$.










share|cite|improve this question









$endgroup$




Let $f: M to M$ define an automorphism on the smooth manifold M.



Given a differential form $omega in Omega^k$ is it true that the de Rham cohomology class of $omega$ and $f^*omega$ are the same? That is, does $[omega]=[f^*omega]$.







differential-geometry de-rham-cohomology






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asked Mar 14 at 6:51









jojojojo

6217




6217







  • 1




    $begingroup$
    Here's another type of example: Consider the antipodal map ($f(x)=-x$) on $S^n$ with $n$ even.
    $endgroup$
    – Ted Shifrin
    Mar 14 at 16:29












  • 1




    $begingroup$
    Here's another type of example: Consider the antipodal map ($f(x)=-x$) on $S^n$ with $n$ even.
    $endgroup$
    – Ted Shifrin
    Mar 14 at 16:29







1




1




$begingroup$
Here's another type of example: Consider the antipodal map ($f(x)=-x$) on $S^n$ with $n$ even.
$endgroup$
– Ted Shifrin
Mar 14 at 16:29




$begingroup$
Here's another type of example: Consider the antipodal map ($f(x)=-x$) on $S^n$ with $n$ even.
$endgroup$
– Ted Shifrin
Mar 14 at 16:29










1 Answer
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No. One example: take the torus $X = mathbbR^2/mathbbZ^2$. The flip-flop on the factors interchanges the closed forms $dx$ and $dy$ which are linearly independent in $H^1(X)$.






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    1 Answer
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    active

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    7












    $begingroup$

    No. One example: take the torus $X = mathbbR^2/mathbbZ^2$. The flip-flop on the factors interchanges the closed forms $dx$ and $dy$ which are linearly independent in $H^1(X)$.






    share|cite|improve this answer









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      7












      $begingroup$

      No. One example: take the torus $X = mathbbR^2/mathbbZ^2$. The flip-flop on the factors interchanges the closed forms $dx$ and $dy$ which are linearly independent in $H^1(X)$.






      share|cite|improve this answer









      $endgroup$















        7












        7








        7





        $begingroup$

        No. One example: take the torus $X = mathbbR^2/mathbbZ^2$. The flip-flop on the factors interchanges the closed forms $dx$ and $dy$ which are linearly independent in $H^1(X)$.






        share|cite|improve this answer









        $endgroup$



        No. One example: take the torus $X = mathbbR^2/mathbbZ^2$. The flip-flop on the factors interchanges the closed forms $dx$ and $dy$ which are linearly independent in $H^1(X)$.







        share|cite|improve this answer












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        answered Mar 14 at 6:54









        hunterhunter

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