algcurves
is_hyperelliptic
test if an algebraic curve is hyperelliptic
Calling Sequence
Parameters
Description
Examples
is_hyperelliptic(f, x, y)
f
-
irreducible polynomial in x and y
x
variable
y
An irreducible algebraic curve fx,y is called rational if the genus is 0. In this case a parametrization can be computed. It is called elliptic if the genus is 1. It is called hyperelliptic if the genus is more than 1 and fx,y is birational to a curve FX,Y with degree(F,Y)=2. In the elliptic or hyperelliptic case a normal form can be computed with Weierstrassform.
If the genus is less than 2, then the curve is not hyperelliptic and the output will be false. If the genus is 2, then the output will be true. For higher genus, the output can be true or false.
withalgcurves:
f≔y2+x5+1
f≔x5+y2+1
g≔y9+2x2y6+2x4y3+x6+y2
h≔y9+3x2y6+3x4y3+x6+y2
is_hyperellipticf,x,y
true
is_hyperellipticg,x,y
false
is_hyperelliptich,x,y
Weierstrassformh,x,y,x0,y0
−x07+7x06−21x05+35x04−35x03+21x02+y02−7x0+2,yy3+x2+1y6+2x2y3+x4+y,−xy3+x2y,−x0−1y0,−x03+3x02−3x0+1
See Also
algcurves[genus]
algcurves[parametrization]
algcurves[Weierstrassform]
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