Explicit equation for the dual hypersurface












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$begingroup$


Let $X$ be a hypersurface in $mathbb P^n$. Assume $X$ is defined by some homogenous polynomial $F$. Then, is there a way to write the equation for $X^vee$ explicitly?



(This is related to my previous question)










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$endgroup$








  • 2




    $begingroup$
    Take a look at en.wikipedia.org/wiki/Dual_curve#Equations and try to mimic the technique there.
    $endgroup$
    – DKS
    Jan 13 at 15:23










  • $begingroup$
    @DKS Thanks! But other from the conic, for hypersurfaces in higher degree, it is not easy to eliminate the parameters. For example, for $X$ defined by $x^3+y^3+z^3=0$, in the way you suggest, we can get the equation for the dual curve $X^{3/2}+Y^{3/2}+Z^{3/2}=0$ . On the other hand, it should be a curve of degree $6$, so I expect an explicit polynomial of degree $6$, which is not clear to me. Is there some way to do this?
    $endgroup$
    – User X
    Jan 13 at 17:15










  • $begingroup$
    Use $(X^{3/2}+Y^{3/2}+Z^{3/2})(X^{3/2}-Y^{3/2}+Z^{3/2})(X^{3/2}+Y^{3/2}-Z^{3/2})(X^{3/2}-Y^{3/2}-Z^{3/2})=0$ ?
    $endgroup$
    – random
    Jan 14 at 12:30










  • $begingroup$
    @random Yes, I think it is in the special case. But in general, it is not easy to get the polynomial from the parametric equations.
    $endgroup$
    – User X
    Jan 17 at 17:38
















0












$begingroup$


Let $X$ be a hypersurface in $mathbb P^n$. Assume $X$ is defined by some homogenous polynomial $F$. Then, is there a way to write the equation for $X^vee$ explicitly?



(This is related to my previous question)










share|cite|improve this question









$endgroup$








  • 2




    $begingroup$
    Take a look at en.wikipedia.org/wiki/Dual_curve#Equations and try to mimic the technique there.
    $endgroup$
    – DKS
    Jan 13 at 15:23










  • $begingroup$
    @DKS Thanks! But other from the conic, for hypersurfaces in higher degree, it is not easy to eliminate the parameters. For example, for $X$ defined by $x^3+y^3+z^3=0$, in the way you suggest, we can get the equation for the dual curve $X^{3/2}+Y^{3/2}+Z^{3/2}=0$ . On the other hand, it should be a curve of degree $6$, so I expect an explicit polynomial of degree $6$, which is not clear to me. Is there some way to do this?
    $endgroup$
    – User X
    Jan 13 at 17:15










  • $begingroup$
    Use $(X^{3/2}+Y^{3/2}+Z^{3/2})(X^{3/2}-Y^{3/2}+Z^{3/2})(X^{3/2}+Y^{3/2}-Z^{3/2})(X^{3/2}-Y^{3/2}-Z^{3/2})=0$ ?
    $endgroup$
    – random
    Jan 14 at 12:30










  • $begingroup$
    @random Yes, I think it is in the special case. But in general, it is not easy to get the polynomial from the parametric equations.
    $endgroup$
    – User X
    Jan 17 at 17:38














0












0








0





$begingroup$


Let $X$ be a hypersurface in $mathbb P^n$. Assume $X$ is defined by some homogenous polynomial $F$. Then, is there a way to write the equation for $X^vee$ explicitly?



(This is related to my previous question)










share|cite|improve this question









$endgroup$




Let $X$ be a hypersurface in $mathbb P^n$. Assume $X$ is defined by some homogenous polynomial $F$. Then, is there a way to write the equation for $X^vee$ explicitly?



(This is related to my previous question)







algebraic-geometry reference-request complex-geometry






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 13 at 11:31









User XUser X

32911




32911








  • 2




    $begingroup$
    Take a look at en.wikipedia.org/wiki/Dual_curve#Equations and try to mimic the technique there.
    $endgroup$
    – DKS
    Jan 13 at 15:23










  • $begingroup$
    @DKS Thanks! But other from the conic, for hypersurfaces in higher degree, it is not easy to eliminate the parameters. For example, for $X$ defined by $x^3+y^3+z^3=0$, in the way you suggest, we can get the equation for the dual curve $X^{3/2}+Y^{3/2}+Z^{3/2}=0$ . On the other hand, it should be a curve of degree $6$, so I expect an explicit polynomial of degree $6$, which is not clear to me. Is there some way to do this?
    $endgroup$
    – User X
    Jan 13 at 17:15










  • $begingroup$
    Use $(X^{3/2}+Y^{3/2}+Z^{3/2})(X^{3/2}-Y^{3/2}+Z^{3/2})(X^{3/2}+Y^{3/2}-Z^{3/2})(X^{3/2}-Y^{3/2}-Z^{3/2})=0$ ?
    $endgroup$
    – random
    Jan 14 at 12:30










  • $begingroup$
    @random Yes, I think it is in the special case. But in general, it is not easy to get the polynomial from the parametric equations.
    $endgroup$
    – User X
    Jan 17 at 17:38














  • 2




    $begingroup$
    Take a look at en.wikipedia.org/wiki/Dual_curve#Equations and try to mimic the technique there.
    $endgroup$
    – DKS
    Jan 13 at 15:23










  • $begingroup$
    @DKS Thanks! But other from the conic, for hypersurfaces in higher degree, it is not easy to eliminate the parameters. For example, for $X$ defined by $x^3+y^3+z^3=0$, in the way you suggest, we can get the equation for the dual curve $X^{3/2}+Y^{3/2}+Z^{3/2}=0$ . On the other hand, it should be a curve of degree $6$, so I expect an explicit polynomial of degree $6$, which is not clear to me. Is there some way to do this?
    $endgroup$
    – User X
    Jan 13 at 17:15










  • $begingroup$
    Use $(X^{3/2}+Y^{3/2}+Z^{3/2})(X^{3/2}-Y^{3/2}+Z^{3/2})(X^{3/2}+Y^{3/2}-Z^{3/2})(X^{3/2}-Y^{3/2}-Z^{3/2})=0$ ?
    $endgroup$
    – random
    Jan 14 at 12:30










  • $begingroup$
    @random Yes, I think it is in the special case. But in general, it is not easy to get the polynomial from the parametric equations.
    $endgroup$
    – User X
    Jan 17 at 17:38








2




2




$begingroup$
Take a look at en.wikipedia.org/wiki/Dual_curve#Equations and try to mimic the technique there.
$endgroup$
– DKS
Jan 13 at 15:23




$begingroup$
Take a look at en.wikipedia.org/wiki/Dual_curve#Equations and try to mimic the technique there.
$endgroup$
– DKS
Jan 13 at 15:23












$begingroup$
@DKS Thanks! But other from the conic, for hypersurfaces in higher degree, it is not easy to eliminate the parameters. For example, for $X$ defined by $x^3+y^3+z^3=0$, in the way you suggest, we can get the equation for the dual curve $X^{3/2}+Y^{3/2}+Z^{3/2}=0$ . On the other hand, it should be a curve of degree $6$, so I expect an explicit polynomial of degree $6$, which is not clear to me. Is there some way to do this?
$endgroup$
– User X
Jan 13 at 17:15




$begingroup$
@DKS Thanks! But other from the conic, for hypersurfaces in higher degree, it is not easy to eliminate the parameters. For example, for $X$ defined by $x^3+y^3+z^3=0$, in the way you suggest, we can get the equation for the dual curve $X^{3/2}+Y^{3/2}+Z^{3/2}=0$ . On the other hand, it should be a curve of degree $6$, so I expect an explicit polynomial of degree $6$, which is not clear to me. Is there some way to do this?
$endgroup$
– User X
Jan 13 at 17:15












$begingroup$
Use $(X^{3/2}+Y^{3/2}+Z^{3/2})(X^{3/2}-Y^{3/2}+Z^{3/2})(X^{3/2}+Y^{3/2}-Z^{3/2})(X^{3/2}-Y^{3/2}-Z^{3/2})=0$ ?
$endgroup$
– random
Jan 14 at 12:30




$begingroup$
Use $(X^{3/2}+Y^{3/2}+Z^{3/2})(X^{3/2}-Y^{3/2}+Z^{3/2})(X^{3/2}+Y^{3/2}-Z^{3/2})(X^{3/2}-Y^{3/2}-Z^{3/2})=0$ ?
$endgroup$
– random
Jan 14 at 12:30












$begingroup$
@random Yes, I think it is in the special case. But in general, it is not easy to get the polynomial from the parametric equations.
$endgroup$
– User X
Jan 17 at 17:38




$begingroup$
@random Yes, I think it is in the special case. But in general, it is not easy to get the polynomial from the parametric equations.
$endgroup$
– User X
Jan 17 at 17:38










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