For which $f in mathbbC[x,y]$, $fy$ is a field generator of $mathbbC(x,y)$?

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Let $f=f(x,y) in mathbbC[x,y]$.



Call an element $F in mathbbC[x,y]$ a field generator of $mathbbC(x,y)$, if there exists $G in mathbbC(x,y)$ such that $mathbbC(F,G)=mathbbC(x,y)$. If $G$ happens to be in $mathbbC[x,y]$, then call $F$ a good field generator. See, for example, this paper.




Is it possible to characterize all $f in mathbbC[x,y]$ such that $fy$ is a field generator?




Examples:
(1) If $f in mathbbC[x]$, then $fy$ is a (good) field generator, since $mathbbC(fy,x)=mathbbC(x,y)$.



(2) If $f=x+y$, then $fy$ is a good field generator, since $mathbbC(fy,y)=mathbbC(xy+y^2,y)=mathbbC(xy,y)=mathbbC(x,y)$.



Any hints and comments are welcome!







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    0
    down vote

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    Let $f=f(x,y) in mathbbC[x,y]$.



    Call an element $F in mathbbC[x,y]$ a field generator of $mathbbC(x,y)$, if there exists $G in mathbbC(x,y)$ such that $mathbbC(F,G)=mathbbC(x,y)$. If $G$ happens to be in $mathbbC[x,y]$, then call $F$ a good field generator. See, for example, this paper.




    Is it possible to characterize all $f in mathbbC[x,y]$ such that $fy$ is a field generator?




    Examples:
    (1) If $f in mathbbC[x]$, then $fy$ is a (good) field generator, since $mathbbC(fy,x)=mathbbC(x,y)$.



    (2) If $f=x+y$, then $fy$ is a good field generator, since $mathbbC(fy,y)=mathbbC(xy+y^2,y)=mathbbC(xy,y)=mathbbC(x,y)$.



    Any hints and comments are welcome!







    share|cite|improve this question
























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      Let $f=f(x,y) in mathbbC[x,y]$.



      Call an element $F in mathbbC[x,y]$ a field generator of $mathbbC(x,y)$, if there exists $G in mathbbC(x,y)$ such that $mathbbC(F,G)=mathbbC(x,y)$. If $G$ happens to be in $mathbbC[x,y]$, then call $F$ a good field generator. See, for example, this paper.




      Is it possible to characterize all $f in mathbbC[x,y]$ such that $fy$ is a field generator?




      Examples:
      (1) If $f in mathbbC[x]$, then $fy$ is a (good) field generator, since $mathbbC(fy,x)=mathbbC(x,y)$.



      (2) If $f=x+y$, then $fy$ is a good field generator, since $mathbbC(fy,y)=mathbbC(xy+y^2,y)=mathbbC(xy,y)=mathbbC(x,y)$.



      Any hints and comments are welcome!







      share|cite|improve this question














      Let $f=f(x,y) in mathbbC[x,y]$.



      Call an element $F in mathbbC[x,y]$ a field generator of $mathbbC(x,y)$, if there exists $G in mathbbC(x,y)$ such that $mathbbC(F,G)=mathbbC(x,y)$. If $G$ happens to be in $mathbbC[x,y]$, then call $F$ a good field generator. See, for example, this paper.




      Is it possible to characterize all $f in mathbbC[x,y]$ such that $fy$ is a field generator?




      Examples:
      (1) If $f in mathbbC[x]$, then $fy$ is a (good) field generator, since $mathbbC(fy,x)=mathbbC(x,y)$.



      (2) If $f=x+y$, then $fy$ is a good field generator, since $mathbbC(fy,y)=mathbbC(xy+y^2,y)=mathbbC(xy,y)=mathbbC(x,y)$.



      Any hints and comments are welcome!









      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Aug 12 at 5:03

























      asked Aug 12 at 3:48









      user237522

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