Elliptic Curves over the Rational Field

New Features:

• Given the real and imaginary periods of a minimal model for an elliptic curve over Q , the intrinsic EllipticCurveFromPeriods will return the curve.

Changes and Removals:

• The extension of John Cremona's database for elliptic curves over Q having conductor up to 300,000 has been installed.
• Renumbered 98 curves in the above database, as requested by John Cremona, to reflect his desired new ordering. The affected curves had conductors between 130,000 and 230,000.

Bug fixes:

• A bug has been fixed that could cause the order of a torsion point on a non-integral elliptic curve over the rationals to be erroneously reported as infinite.

• Saving a workspace when the elliptic curve database is around no longer causes the database to return read errors thereafter.

• A bug has been fixed in the rank computation for elliptic curves with no rational 2-torsion points. This bug could cause some covering quartics to be erroneously discarded as not contributing to the 2-Selmer group, which in turn could cause the upper bound on the rank to be incorrectly computed. In most instances an error message or warning would highlight that this had occurred.

• Significant improvements and bug fixes have been made in EightDescent.

• A problem in TwoDescent has been fixed: for curves of large conductor having one nontrivial 2-torsion point, computations got stuck due to bad handling of power products.