Change log for Magma V2.15-4 (Released 14/1/2009)

Algebraic Curves

·IsNodal checks for plane curves have been corrected to work for (geometrically) non-reduced curves. Bug reported by A. Brumer.

·The Genus crash over finite fields has been fixed (see note in the Matrices section above).

Arithmetic Geometry

·A bug with EisensteinProjection of a modular form that was already in an EisensteinSubspace has been fixed.

Commutative Algebra

·A crash in primary decomposition of positive dimensional ideals has been fixed.

·A hang in Groebner basis computation for ideals over GF(2) with a large number of variables has been fixed. Reported by J. Erickson.

Galois Groups

·The computation of Galois Groups over function fields of positive characteristic has been switched off due to too many problems. A rewrite is in progress.

Group Representations

·When dealing with a natural permutation module of a permutation group, the map returned by the Representation function now uses methods equivalent to using PermutationMatrix rather than using generic group homomorphism methods. Suggested by Markus Grassl.

Groups

·A trap for large cyclic components has been installed in the FPGroup function for groups of type GrpAb. Reported by Eamonn O'Brien.

·A crash which occurred when constructing the maximal subgroups of L(10, 2) has been fixed. Reported by Colva Roney-Dougal.

·A bug in filtering subgroups produced by the Subgroups function when the new method for expanding maximal subgroups is used has been fixed. Bug reported by Florian Moeller.

Matrices

·A bug involving matrices of polynomials over finite fields (coming out of calls to Genus) has been fixed. Reported by A. Brumer.