Opened 10 years ago

Last modified 8 years ago

## #12880 closed defect

# Inconsistent domain, codomain and parent in EllipticCurveIsogeny — at Initial Version

Reported by: | nthiery | Owned by: | was |
---|---|---|---|

Priority: | minor | Milestone: | sage-6.3 |

Component: | elliptic curves | Keywords: | isogeny |

Cc: | sage-combinat, pbruin, defeo, sbesnier | Merged in: | |

Authors: | Reviewers: | ||

Report Upstream: | N/A | Work issues: | |

Branch: | Commit: | ||

Dependencies: | Stopgaps: |

### Description

In the following example, the domain and codomain of phi does not match with that of its parent::

sage: sage: E = EllipticCurve(j=GF(7)(0)) sage: phi = EllipticCurveIsogeny(E, [E(0), E((0,1)), E((0,-1))]) sage: phi.parent() Set of Morphisms from Abelian group of points on Elliptic Curve defined by y^2 = x^3 + 1 over Finite Field of size 7 to Abelian group of points on Elliptic Curve defined by y^2 = x^3 + 1 over Finite Field of size 7 in Category of hom sets in Category of Schemes sage: phi.parent().domain() Abelian group of points on Elliptic Curve defined by y^2 = x^3 + 1 over Finite Field of size 7 sage: phi.domain() Elliptic Curve defined by y^2 = x^3 + 1 over Finite Field of size 7 sage: phi.parent().codomain() Abelian group of points on Elliptic Curve defined by y^2 = x^3 + 1 over Finite Field of size 7 sage: phi.codomain() Elliptic Curve defined by y^2 = x^3 + 1 over Finite Field of size 7

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