Change log for Magma V2.23-3 (Released 10/8/2017)

FP Groups

·A bug in the code for the intrinsic IsInfiniteFPGroup which caused it to crash when searching for low index subgroups in the case of 'difficult' fp-groups has been fixed.

·An additional parameter Hard has been installed for the intrinsic IsInfiniteFPGroup which, if set to true, invests additional effort into trying to show that the group is infinite. The default setting for Hard is false.

FP Semigroups

·A crash when creating quotients of FP semigroups or FP monoids with an empty relation list has been fixed.

Finite Groups

·A crash when accessing the orders and class lengths of a subgroup lattice has been fixed.

Invariant Rings

·A crash in SecondaryInvariants after setting the primary invariants manually has been fixed. Reported by A. Thevis.

Lattices

·The third returned value of LLLGram was essentially random in the indefinite case, not the rank as specified. Reported by E. Costa.

Lie Theory

·A crash in the intrinsic Plethysm which computes the decomposition polynomial of the plethysm of a Lie algebra representation has been fixed. The crash occurred when given the empty partition. Reported by R. Zeier.

·A crash in the action of a lie algebra on elements of submodules of symmetric and exterior power modules has been fixed.

Matrices

·The base algorithm for matrix multiplication in moderately small dimension has been improved for matrices over GF(2) and GF(3).

Matrix Groups

·As the result of recent improvements made to the intrinsics Normaliser, IsConjugate and related functions for matrix groups defined over finite fields, these intrinsics were accidentally disabled for matrix groups over finite rings such as Z/nZ. These functions have now been restored for matrix groups over finite rings other than GF(q). Reported by A. Sutherland.

Real and Complex Fields

·A hang and some accuracy errors in complex root finding have been fixed. Reported by J. Klueners.

Series Rings

·An error from the Roots computation for polynomials over infinite precision series rings about not enough precision available has been resolved by the fixing of a bug in the computation of GCDs of polynomials over series rings.

System

·The error reporting has been improved in the case that incompatible .sig files are used in a newer version of Magma. Reported by I. Qureshi.