General case of a result in differential geometry

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Let $W subset Bbb R^n$ open and $F:W to Bbb R$, $F$ is $C^infty$ and $alt b in F(W)$ so that $L=F^-1([a,b])$ is compact and $nabla F(p) ne 0$ for every $p in L$



By taking the field $X = frac nabla F^2 $ then the flow $φ^X_b-a$ gives us a diffeomormphism between $F^-1(a)$ and $F^-1(b)$.



My question is if we can generalise this for $Bbb R^k$ instead of $Bbb R$?







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    up vote
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    favorite












    Let $W subset Bbb R^n$ open and $F:W to Bbb R$, $F$ is $C^infty$ and $alt b in F(W)$ so that $L=F^-1([a,b])$ is compact and $nabla F(p) ne 0$ for every $p in L$



    By taking the field $X = frac nabla F^2 $ then the flow $φ^X_b-a$ gives us a diffeomormphism between $F^-1(a)$ and $F^-1(b)$.



    My question is if we can generalise this for $Bbb R^k$ instead of $Bbb R$?







    share|cite|improve this question























      up vote
      2
      down vote

      favorite









      up vote
      2
      down vote

      favorite











      Let $W subset Bbb R^n$ open and $F:W to Bbb R$, $F$ is $C^infty$ and $alt b in F(W)$ so that $L=F^-1([a,b])$ is compact and $nabla F(p) ne 0$ for every $p in L$



      By taking the field $X = frac nabla F^2 $ then the flow $φ^X_b-a$ gives us a diffeomormphism between $F^-1(a)$ and $F^-1(b)$.



      My question is if we can generalise this for $Bbb R^k$ instead of $Bbb R$?







      share|cite|improve this question













      Let $W subset Bbb R^n$ open and $F:W to Bbb R$, $F$ is $C^infty$ and $alt b in F(W)$ so that $L=F^-1([a,b])$ is compact and $nabla F(p) ne 0$ for every $p in L$



      By taking the field $X = frac nabla F^2 $ then the flow $φ^X_b-a$ gives us a diffeomormphism between $F^-1(a)$ and $F^-1(b)$.



      My question is if we can generalise this for $Bbb R^k$ instead of $Bbb R$?









      share|cite|improve this question












      share|cite|improve this question




      share|cite|improve this question








      edited Aug 2 at 17:51









      John Ma

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      asked Aug 2 at 16:18









      Amontillado

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          1 Answer
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          No.



          For example, think of a regular curve (so $nabla gamma neq 0$) $gamma : (-epsilon, epsilon) to mathbb R^2$ which has a self intersection at $a=(0,0)in mathbb R^2$. Then $gamma^-1(a)$ has more than one points while $gamma^-1(b)$ has only one point in general.






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            1 Answer
            1






            active

            oldest

            votes








            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            1
            down vote



            accepted










            No.



            For example, think of a regular curve (so $nabla gamma neq 0$) $gamma : (-epsilon, epsilon) to mathbb R^2$ which has a self intersection at $a=(0,0)in mathbb R^2$. Then $gamma^-1(a)$ has more than one points while $gamma^-1(b)$ has only one point in general.






            share|cite|improve this answer

























              up vote
              1
              down vote



              accepted










              No.



              For example, think of a regular curve (so $nabla gamma neq 0$) $gamma : (-epsilon, epsilon) to mathbb R^2$ which has a self intersection at $a=(0,0)in mathbb R^2$. Then $gamma^-1(a)$ has more than one points while $gamma^-1(b)$ has only one point in general.






              share|cite|improve this answer























                up vote
                1
                down vote



                accepted







                up vote
                1
                down vote



                accepted






                No.



                For example, think of a regular curve (so $nabla gamma neq 0$) $gamma : (-epsilon, epsilon) to mathbb R^2$ which has a self intersection at $a=(0,0)in mathbb R^2$. Then $gamma^-1(a)$ has more than one points while $gamma^-1(b)$ has only one point in general.






                share|cite|improve this answer













                No.



                For example, think of a regular curve (so $nabla gamma neq 0$) $gamma : (-epsilon, epsilon) to mathbb R^2$ which has a self intersection at $a=(0,0)in mathbb R^2$. Then $gamma^-1(a)$ has more than one points while $gamma^-1(b)$ has only one point in general.







                share|cite|improve this answer













                share|cite|improve this answer



                share|cite|improve this answer











                answered Aug 2 at 17:54









                John Ma

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