Change log for Magma V2.28-26 (Released 17/7/2025)

Algebraic Number Fields

·A crash has been fixed in the computation of UnitGroups.

·A crash in ext<> for number fields when given a sequence of integers has been fixed. Reported by Lewis Combes.

Elliptic Curves

·The functions WeilPairing(P, Q, n) and TatePairing(P, Q, n) now first attempt to coerce Q into the parent of P if these parents are not identical. Issue reported by Sachi Hashimoto.

Hyperelliptic Curves

·The function HeightConstant now sometimes gives a better bound for the difference between naive and canonical height on Jacobians of genus 2 curves, for instance in Example 6.2 of the recent paper of Garcia-Fritz and Pasten. Improved code supplied by Steffen Mueller and Michael Stoll.

Integers

·Fixed a bug with ShiftRight that would return an answer one too low if a negative number was shifted and the result should have been exact.

Language

·A crash in assignment (in a certain situation involving multiple RHS values) has been fixed. Reported by Antoine Joux.

Lattices

·A crash in ClosestVector involving a lattice with very large entries in its basis matrix has been fixed. Reported by Markus Kirschmer.

·A crash in HKZ with the Unique parameter and a transformation matrix matrix has been fixed. Reported by Hao Guo.

Matrices

·A bad slowdown when computing the Smith Normal Form with transformation matrices for a sparse matrix defined over a ring which is not the integer ring has been fixed.

Matrix Groups

·An incorrect result for CompositionTreeCompositionFactors applied to the Lyons group has been fixed. Reported by David Craven.

·A new optional parameter Sign has been added to DoubleCoverSymmetricGroup which is the opposite of the existing Type. Added by Derek Holt after discussion with David Craven.

Polynomial Rings

·A crash in Discriminant (arising from IsEasySnAn) for very large integer polynomials has been fixed. The algorithm has been sped up at the same time. Reported by Nick Katz.