If a smooth map between manifolds is injective, is the induced map on the tangent spaces injective too?












3












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If $phi:Mlongrightarrow N$ is an injective smooth map between two manifolds, then is $dphi_m:M_mlongrightarrow N_{phi(m)}$, the induced map between the tangent spaces injective too?



I tried the following : If $vin M_m$ is such that $dphi_m(v)=0$, then for all $g$, $C^{infty}$ function in a neighbourhood of $phi(m)$, $dphi_m(v)(g)=0$, that is $v(gcircphi)=0$ for all such $g$. From this can we conclude that $v$ is the $0$ tangent vector.



I got this doubt when I was trying to understand the definition of an immersion. I was wondering if $phi$ being injective will automatically make it an immersion.










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$endgroup$

















    3












    $begingroup$


    If $phi:Mlongrightarrow N$ is an injective smooth map between two manifolds, then is $dphi_m:M_mlongrightarrow N_{phi(m)}$, the induced map between the tangent spaces injective too?



    I tried the following : If $vin M_m$ is such that $dphi_m(v)=0$, then for all $g$, $C^{infty}$ function in a neighbourhood of $phi(m)$, $dphi_m(v)(g)=0$, that is $v(gcircphi)=0$ for all such $g$. From this can we conclude that $v$ is the $0$ tangent vector.



    I got this doubt when I was trying to understand the definition of an immersion. I was wondering if $phi$ being injective will automatically make it an immersion.










    share|cite|improve this question











    $endgroup$















      3












      3








      3





      $begingroup$


      If $phi:Mlongrightarrow N$ is an injective smooth map between two manifolds, then is $dphi_m:M_mlongrightarrow N_{phi(m)}$, the induced map between the tangent spaces injective too?



      I tried the following : If $vin M_m$ is such that $dphi_m(v)=0$, then for all $g$, $C^{infty}$ function in a neighbourhood of $phi(m)$, $dphi_m(v)(g)=0$, that is $v(gcircphi)=0$ for all such $g$. From this can we conclude that $v$ is the $0$ tangent vector.



      I got this doubt when I was trying to understand the definition of an immersion. I was wondering if $phi$ being injective will automatically make it an immersion.










      share|cite|improve this question











      $endgroup$




      If $phi:Mlongrightarrow N$ is an injective smooth map between two manifolds, then is $dphi_m:M_mlongrightarrow N_{phi(m)}$, the induced map between the tangent spaces injective too?



      I tried the following : If $vin M_m$ is such that $dphi_m(v)=0$, then for all $g$, $C^{infty}$ function in a neighbourhood of $phi(m)$, $dphi_m(v)(g)=0$, that is $v(gcircphi)=0$ for all such $g$. From this can we conclude that $v$ is the $0$ tangent vector.



      I got this doubt when I was trying to understand the definition of an immersion. I was wondering if $phi$ being injective will automatically make it an immersion.







      differential-geometry manifolds






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      edited Feb 21 '14 at 0:53









      Brian Fitzpatrick

      21.1k42958




      21.1k42958










      asked Feb 11 '14 at 7:04









      gradstudentgradstudent

      1,293720




      1,293720






















          2 Answers
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          6












          $begingroup$

          The answer is no. Let $phi:mathbb Rrightarrowmathbb R^2$ be $phi(t)=(t^3,t^9)$. Then the derivative at $t=0$ is not injective.






          share|cite|improve this answer









          $endgroup$









          • 3




            $begingroup$
            You can also use the function $f(x)=x^3$ from the real line to itself.
            $endgroup$
            – Moishe Cohen
            Feb 11 '14 at 10:33



















          -1












          $begingroup$

          If the map $phi:Mlongrightarrow N$ is an diffeomorphism then $dphi_m:M_mlongrightarrow N_{phi(m)}$ is an isomorphism.






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            2 Answers
            2






            active

            oldest

            votes








            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            6












            $begingroup$

            The answer is no. Let $phi:mathbb Rrightarrowmathbb R^2$ be $phi(t)=(t^3,t^9)$. Then the derivative at $t=0$ is not injective.






            share|cite|improve this answer









            $endgroup$









            • 3




              $begingroup$
              You can also use the function $f(x)=x^3$ from the real line to itself.
              $endgroup$
              – Moishe Cohen
              Feb 11 '14 at 10:33
















            6












            $begingroup$

            The answer is no. Let $phi:mathbb Rrightarrowmathbb R^2$ be $phi(t)=(t^3,t^9)$. Then the derivative at $t=0$ is not injective.






            share|cite|improve this answer









            $endgroup$









            • 3




              $begingroup$
              You can also use the function $f(x)=x^3$ from the real line to itself.
              $endgroup$
              – Moishe Cohen
              Feb 11 '14 at 10:33














            6












            6








            6





            $begingroup$

            The answer is no. Let $phi:mathbb Rrightarrowmathbb R^2$ be $phi(t)=(t^3,t^9)$. Then the derivative at $t=0$ is not injective.






            share|cite|improve this answer









            $endgroup$



            The answer is no. Let $phi:mathbb Rrightarrowmathbb R^2$ be $phi(t)=(t^3,t^9)$. Then the derivative at $t=0$ is not injective.







            share|cite|improve this answer












            share|cite|improve this answer



            share|cite|improve this answer










            answered Feb 11 '14 at 7:12









            Brian FitzpatrickBrian Fitzpatrick

            21.1k42958




            21.1k42958








            • 3




              $begingroup$
              You can also use the function $f(x)=x^3$ from the real line to itself.
              $endgroup$
              – Moishe Cohen
              Feb 11 '14 at 10:33














            • 3




              $begingroup$
              You can also use the function $f(x)=x^3$ from the real line to itself.
              $endgroup$
              – Moishe Cohen
              Feb 11 '14 at 10:33








            3




            3




            $begingroup$
            You can also use the function $f(x)=x^3$ from the real line to itself.
            $endgroup$
            – Moishe Cohen
            Feb 11 '14 at 10:33




            $begingroup$
            You can also use the function $f(x)=x^3$ from the real line to itself.
            $endgroup$
            – Moishe Cohen
            Feb 11 '14 at 10:33











            -1












            $begingroup$

            If the map $phi:Mlongrightarrow N$ is an diffeomorphism then $dphi_m:M_mlongrightarrow N_{phi(m)}$ is an isomorphism.






            share|cite|improve this answer











            $endgroup$


















              -1












              $begingroup$

              If the map $phi:Mlongrightarrow N$ is an diffeomorphism then $dphi_m:M_mlongrightarrow N_{phi(m)}$ is an isomorphism.






              share|cite|improve this answer











              $endgroup$
















                -1












                -1








                -1





                $begingroup$

                If the map $phi:Mlongrightarrow N$ is an diffeomorphism then $dphi_m:M_mlongrightarrow N_{phi(m)}$ is an isomorphism.






                share|cite|improve this answer











                $endgroup$



                If the map $phi:Mlongrightarrow N$ is an diffeomorphism then $dphi_m:M_mlongrightarrow N_{phi(m)}$ is an isomorphism.







                share|cite|improve this answer














                share|cite|improve this answer



                share|cite|improve this answer








                edited Dec 8 '18 at 17:19









                dantopa

                6,45942242




                6,45942242










                answered Feb 20 '14 at 9:43









                ramya msuramya msu

                162




                162






























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