id summary reporter owner description type status priority milestone component resolution keywords cc merged author reviewer upstream work_issues branch commit dependencies stopgaps
5065 elliptic curve torsion subgroup doesn't know its identity boothby "The torsion subgroup of an elliptic curve appears to be quite broken -- it barfs when trying to coerce in 0,
{{{
sage: E = EllipticCurve(1)
sage: T = E.torsion_subgroup()
sage: T(0)
...
...
TypeError: Argument x (= 0) is of wrong type.
}}}
further, it returns a mysterious 1 when coercing in a 1
{{{
sage: a = T(1); a
1
sage: b = T.gens()[0]-T.gens()[0]; b
(0 : 1 : 0)
sage: a+b
TypeError: unsupported operand parent(s) for '+': 'Abelian group of points on Elliptic Curve defined by y^2 + x*y + y = x^3 - 19*x + 26 over Rational Field' and 'Torsion Subgroup isomorphic to Multiplicative Abelian Group isomorphic to C6 x C2 associated to the Elliptic Curve defined by y^2 + x*y + y = x^3 - 19*x + 26 over Rational Field'
}}}
Yet, it's all cool with the original curve.
{{{
sage: E(0)
(0 : 1 : 0)
sage: E(1)
...
...
TypeError: v (=(1,)) must have 3 components
sage:
}}}
" defect closed minor sage-duplicate/invalid/wontfix elliptic curves duplicate N/A