Change log for Magma V2.23-5 (Released 20/10/2017)

Arithmetic Geometry

·The function TwoCoverDescent has been improved. Also, a new parameter Points has been added, which can be set to a set of rational points on the curve, to be used for an early exit when the given points exhaust the upper bound for the Selmer set computed so far.

·The 3rd return value of the function AutomorphismGroup has been fixed for hyperelliptic curves.

Coding Theory

·MacWilliamsTransform has been considerably sped up.

Cyclotomic Fields

·A deletion problem with cyclotomic fields has been fixed. This was seen during computations with character tables and class groups.

Galois Theory

·An internal problem with SolveByRadicals has been fixed. Reported by M. Grassl.

Group Theory

·Various improvements have been made to the large matrix group code.

Hecke Characters

·Some problems with coercion of the trivial character were fixed, and the code now caches ideals to ensure compatability.

Integers

·The upper limit on PrimesUpTo has been changed so that a crash no longer ensues. Reported by M. Kirschmer.

Lattices

·The crash involving BKZ intrinsic over the rational field has been fixed.

Polynomial Rings

·New parameter DegreeLimit:=D added to Factorization for univariate polynomials so that only irreducible factors with degree at most the given bound D are returned (this can lead to large speedups for certain base rings). The general factorization algorithm for univariate polynomials over Z or Q has also been sped up. Requested by E. GonzÃ¡lez-JimÃ©nez.

System

·The parent of an extended type is now the power structure of ECat, not the power structure of Cat. Reported by T. Dokchitser.