Change log for Magma V2.28-18 (Released 7/1/2025)

Algebraic Number Fields

·Recomputation of maximal orders using the Montes Algorithm has been avoided for example, when computing ClassGroup. Reported by Noam D. Elkies.

·The decision on which Maximal order algorithm to use for number fields has been made more reliable. Reported by Noam D. Elkies.

Algebras

·Center is no longer available for AlgInfD unless the algebra also inherits from Rng. This removes the Ambiguous Signature match which was occurring. Reported by Csaba Schneider.

Associative Algebras

·For an algebra of type AlgAssV the intrinsic WriteOver is not the inverse of RepresentationMatrixOfMatrix. Indeed, if M := RepresentationMatrixOfMatrix([a]), then WriteOver(M,A) returns a, not [a]. Therefore, instances of WriteOver in the intrinsics ConjugacyClasses, CharacterTable, IsConjugate and InvariantForms in the file Hermitian/automorphisms.m have been changed to WriteOverMatrix.

Groups

·A crash using Extension with GrpPerm argument when the underlying group of the cohomology module is not a permutation or matrix group has been trapped to give a runtime error with a more useful error message. Bug reported by Steve Humphries.

·The operator subset has been improved for PC groups to avoid a blowup in memory and time usage when applied to the same group many times. Issue reported by Derek Holt.

·A crash in IsConjugate called on subgroups of a quaternionic matrix group has been fixed. The problem was in computing the orbit of a 1-dimensional subspace of the natural RSpace of the group, so any problems with such computations should now be trouble free. Bug reported by Don Taylor.

Lattices

·A bug in SuccessiveMinima where the lattice basis had wide ranging bit lengths has been fixed. Reported by Wouter Castryck.

Local Rings

·A fix has been made to AllExtensions when the degree of the extensions is divisible by the prime of the input ring. Reported by Nuno Freitas.

Modular Forms

·A crash in HeilbronnMerel(N) for large N (coming out of a call to HeckeOperator) has been fixed. Reported by Drew Sutherland.

Representation Theory

·An error in IrreducibleModules when running in the Magma Calculator has been fixed. Reported by Dikran Karagueuzian.

Schemes

·The function ProjectiveSpace has been fixed in the case that a grading is given, so that the grevlexw monomial order is now used with that grading to define the underlying polynomial ring. This means that underlying Groebner bases are often smaller and more quickly computed than previously. In particular, JacobianSubrankScheme is much faster for some types of input involving graded spaces. Example input provided by Muhammad Imran Qureshi.

System

·A flag has been added to warn when a new package intrinsic overrides an older intrinsic; the corresponding set/get intrinsics are SetWarnIntrinsicOverride and GetWarnIntrinsicOverride. Currently it defaults to false (no warning). The warning message when overriding an intrinsic now prints the extended types of the intrinsic arguments where appropriate.

·HasSignature no longer crashes when the intrinsic has signatures using tilde parameters.