Change log for Magma V2.13-7 (Released 4/12/2006)

Algebraic Geometry

·A bug in the function TangentCone has been fixed.

Algebraically Closed Fields

·A bug in algebraically closed fields defined over finite fields of small characteristic has been fixed. Reported by H. Baarnhielm.

Codes

·A bug in GriesmerMinimumWeightBound has been fixed.

·Bugs associated with linear codes of length 0 have been fixed by banning the creation of such codes. Bug report from Markus Grassl.

·A bug in the Magma level printing of cyclic codes over 4 has been fixed. Reported by G. Nebe.

Commutative Algebra

·A leak in computing Groebner bases over the rational field has been fixed.

Elliptic Curves

·A bug has been fixed in TwoSelmerGroup for elliptic curves over number fields (which manifested itself for fields highly ramified at 2). Reported by Christian Wuthrich.

·In TwoSelmerGroup for elliptic curves over function fields, a further adjustment has been made to the precision for local calculations.

·A speed-up in ThreeDescent has been made.

·A bug that prevented IsPoint(E, x) and Points(E, x) from working for elliptic curves over local fields has been fixed. Reported by William Hart.

·A crash in the rank computation for certain curves with large generators has been fixed.

·A bug in p-adic root-finding which caused crashes in IsDivisibleBy(P,n) has been fixed. This is a preliminary fix and further changes to improve the efficiency of division over local fields (particularly as regards the required precision) will appear in the next release. Reported by William Hart.

·A bug in Twists(E) for supersingular curves over finite fields of characteristic 2 has been fixed. Reported by Ben Smith.

GaloisGroups

·A bug in the Galois group package that would occasionally introduce an infinite loop using more and more memory has been fixed.

Groups

·An inefficiency in computing homomorphisms with domain a permutation group has been rectified. This inefficiency sometimes created serious memory blow-outs when mapping into an FP-group. Bug report from Marston Conder.

·The intrinsic SmallGroupProcess has been changed to not give an error when there are no groups in the database that satisfy the given conditions. In this case an empty process is returned. Bug report from Markus Grassl.

·The permutation group predicate IsAltsym has been modified to deal more efficiently with regular groups. This should reduce the time to get the order of a regular group.

·A bug when computing MaximalSubgroups of PSU(3,25) has been fixed.

·A bug in CharacterTable has been fixed. This bug produced the error messages "Problem with covering" and "WRONG - Sum of degree squares is not group order". Bug reported by Markus Grassl.

Lie Theory

·A bug in StandardRootSystem that accidently swapped root systems of types C and D has been fixed. Bug reported by Sait Halicioglu.

·A bug has been fixed that allowed creation of invalid twisted root data in certain cases. Bug reported by H. Baarnhielm.

Matrices

·A slowdown in multiplication of matrices over small finite fields of characteristic 2 has been fixed.

Modular Forms

·Two bugs in the computation of Eisenstein forms have been fixed: (a) some forms were assigned to the wrong character (reported by Ethan Smith), and (b) some forms were missing because not all conjugates of the character were considered.

Number Fields

·A bug in the computation of the index between two absolute orders that could cause memory corruption has been fixed.

Series Rings

·The Factorization of a polynomial over a series ring now has no more precision than the input polynomial.