Change log for Magma V2.17-8 (Released 27/5/2011)

Algebras

·A missing error check has been inserted. Reported by C. Quitte.

Elliptic Curves

·Allow QuarticReduce (of 2-covers) to work on cubic inputs more readily. Reported by T. A. Fisher.

Function Fields

·Maximal order computation in Artinâ€“Schreier extensions has been improved.

·Construction of Function fields using polynomials over non-fields has been expanded and fixed.

Groebner Bases

·A crash involving a very large number of input polynomials has been fixed. Reported by F. Levy-dit-Vehel.

Group Characters and Representations

·An error when computing the character table of a few groups where the full character table was not found has been fixed.

·It is now possible to conjugate a character of group G by an element of of the automorphism group of G without getting a crash.

Groups

·A bug in ClassicalSylow applied to a 2 dimensional unitary group has been fixed. Bug reported by E. O'Brien.

·A crash in the evaluation of homomorphisms with domain a matrix group has been fixed. Bug reported by T. Dokchitser.

·A bug when using sets of pc-groups with universe PowerGroup of a specified supergroup has been fixed. Bug reported by D. Howden.

·A crash when computing double cosets in an fp-group, where one of the subgroups is the whole group, has been fixed.

·A crash when using the class action map of a group automorphism group has been fixed. Bug reported by D. Howden.

·A crash when computing image and/or kernel of a badly defined group homomorphism has been fixed. Bug hit by unknown calculator user.

·Group homomorphisms with domain a rewrite system or automatic were broken and are now fixed. Bug reported by D. Holt.

·A new version of the matrix group composition tree code from E. O'Brien has been installed.

Integer Ring

·A new function GetStoredFactors returns the sequence of currently stored factors used in integer factorization.

Lie Theory

·Fix a problem in IsSplittingCartanSubalgebra for matrix Lie algebras.

·Add support for SplittingCartanSubalgebra, IsSplitToralSubalgebra, and SplitToralSubalgebra for matrix Lie algebras. Omission reported by A. Previtali.

·Improved the interface to the Littlewood-Richardson tensor procedures for Lie representation decompositions (aka "weight multisets"), and add a number of checks. In particular, LittlewoodRichardsonTensor now either takes partitions (or partition multisets) and returns a partition multiset; or it takes two weight multisets and returns a weight multiset; or it takes a root datum and two highest weights and returns a weight multiset. The old (incorrect) behaviour remains temporarily available as LittlewoodRichardsonTensorOld. Crash reported by C. Quitte.

Matrices

·Solution and Rowspace now work properly for matrices over exterior algebras. Reported by M. Kirschmer.

Matrix Algebras

·Fix a bug in meet for matrix algebras that could occasionally lead to a crash due to an incorrect return type.

Permutation Groups

·The transitive group database for degree 32 has been added.

·Some minor leaks in the conjugacy classes computations for permutation groups have been fixed

Polynomial Rings

·A missing error check for overflow in polynomial powering has been added.

Series Rings

·A check has been added in Log to check whether the logarithm of the first coefficient can be taken. Reported by E. Thome.

·Some precision handling in extensions of series fields has been improved when precision of an element is infinite.

System

·A crash when recovering from runtime errors has been fixed. Reported by C. Puodzius.