Change log for Magma V2.17-4 (Released 4/2/2011)

Algebraic Number Fields

·A fix has been made to Subfields of algebraic number fields in relative representation.

·A fix has been made to memory management for class group computations.

·A fix has been made to GaloisGroup for reducible polynomials over algebraic number fields.

·The prime chosen for the creation of lattices of subfields has been changed. The old prime could produce splitting fields too large to be useful. Reported by J. KlÃ¼ners.

·A bug in PellEquation has been fixed. NormEquation was called with the wrong parameters. Reported and fixed by N. Bruin.

·The changed signature for GetAssertions caused a runtime error in certain computations of Galois groups.

Algebras

·Argument checking in BasisProduct for structure constant algebras has been improved.

·A crash in MaximalIdeals for group algebras has been fixed. Reported by S. Humphries.

Commutative Algebra

·An incorrect result for ColonIdeal for ideals with gradings has been fixed. Reported by E. Rains.

Convex Polytopes

·The ID numbers used by PolytopeReflexiveFanoDim3 now coincide with the PALP database, with the exception that PALP indexes from 0..4318, whilst Magma indexes from 1..4319.

Databases of Groups

·A crash (due to incomplete porting of the small groups database to the new garbage collection scheme) has been fixed. Reported by M. Newman.

Function Fields

·A problem in the ext<...> constructor for function fields has been fixed: it would cause an internal error on zero (or constant) polynomials.

Graphs

·A crash has been fixed in the MultiGraph constructor when using an indexed set to describe the edges. Reported by C. Quitte.

Group Representations

·A bug in the IrreducibleModules function has been fixed. Reported by U. Thiel.

Groups

·A bug in the implementation of the IsPerfect filter for the Subgroups intrinsic, which allowed the return of subgroups that were not perfect, has been fixed. Reported by D. Holt.

·A crash to do with degree 2 orthogonal groups over finite fields has been fixed.

·A crash in the permutation group Jellyfish functions has been fixed. Reported by E. O'Brien.

L-Series

·Fixed the definition of the LSeries of a Hilbert modular form at bad primes

·Fixed a series-precision problem in LTaylor

Lie Theory

·A bug in the map returned by the quo<...> constructor for Matrix Lie algebras has been fixed: it would return objects of incorrect type. Reported by S. Murray.

·The performance of BruhatLessOrEqual, BruhatDescendants, KLPolynomial and RPolynomial has been greatly improved. Moreover, these methods now apply to elements of Coxeter groups presented as permutation groups, fp groups, or matrix groups.

Module Theory

·A bug in Submodules with codimension limit (coming from a call to LowIndexNormalSubgroups) has been fixed. Reported by T. Kliem.

Polynomial Rings

·Creating HenselProcess objects no longer causes crashes.

Series Rings

·Reverse of a series no longer loses a digit of precision. Reported by A. Previtali.

·In fixed-precision series rings, evaluating a full-precision series at a term with valuation zero no longer reduces the result to have no precision. Reported by A. Lauder.