Change log for Magma V2.15-11 (Released 7/7/2009)

Arithmetic Geometry

·Fixed a regression in ChabautyEquations, which affected the results returned in the elliptic curve Chabauty routines in certain rare conditions. Reported and fixed by N. Bruin.

Associative Arrays

·A bug in assignment for associative arrays of aggregates has been fixed. Reported by N. Bruin.

Coding Theory

·Fixed a memory leak in the minimum weight computation for some quasi-cyclic codes. Reported by N. Aydin and M. Grassl.

Commutative Algebra

·A bug in Homogenization has been fixed. Reported by M. Grassl.

·A crash in computing random elements of a chain of univariate quotient rings has been fixed. Reported by M. Javadi.

·A missing error check in FieldOfFractions for proper ideals of univariate polynomials has been inserted. Reported by B. Wardemann.

·An incorrect result in IsPrime has been fixed. Reported by J. Kraemer.

Congruence Subgroups

·Fixed a bug in equivalence testing of cusps that would occasionally incorrectly decide that two equivalent cusps were inequivalent. Reported by R. Perlis.

GaloisGroup

·A couple of problems with leading coefficients in reducible polynomials has been fixed. Reported by A-S. Elsenhans.

·A problem with linear factors in reducible polynomials has been fixed. Reported by A-S. Elsenhans.

Groups

·The code for RandomProcess with alternative supplied generators no longer tries to verify that the generators are in the group when the group is a permutation or matrix group. Response to complaint from E. O'Brien.

·Two functions for converting small finitely presented groups to other types have been added. These are PermutationGroup and PCGroup.

·The IsTrivial function for matrix groups over infinite fields has been fixed to use the fact that groups without generators are trivial. Bug reported by E. O'Brien.

·A bug in IsNilpotent and LowerCentralSeries for matrix groups over infinite fields has been avoided by more error checking. Bug reported by E. O'Brien.

·Generators for the special and general linear groups over the integers have been coded into Magma. Requested by E. O'Brien.

·A bug in the filtering of subgroups when using the Subgroups family of functions with the OrderEqual or OrderDividing parameters set has been fixed. The bug led to classes of subgroups being missed.

·User defined homomorphisms with domain a pc-group have been revised to allow preimage computations. Reported by D. Holt.

Lattices

·A bug in IsIsometric has been fixed. Reported by D. Kohel.

Module Theory

·A bug in Submodules, when the number of submodules was overflowing a limit and causing and incorrect answer, has been fixed. Reported by E. O'Brien.

Modules over Dedekind Domains

·A matrix was inverted over the wrong ring potentially resulting in incorrect results in the intersection of two modules. This would only occur if the modules are created over a Magma-known Euclidean quadratic field. Reported by M. Sengun.

Number Fields

·An overzealous assertion in the code has been corrected. This problem could on rare occasions case an internal error while mapping elements into residue class fields. Reported by H. Nover.

Quadratic Fields

·Using Euclidean operations in QuadraticField(-3) would result in the printing of several lines containing only 1. Bug reported by M. Sengun.

·A crash in printing of orders of quadratic fields has been fixed. Bug reported by M. Sengun.

Sequences

·A bug in comparison of large sequences that use the range specifier has been fixed. Reported by J. Kimberley.

Series Rings

·Fixed the creation of an unramified extension by a polynomial not over the constant field.