Change log for Magma V2.16-13 (Released 6/10/2010)

Algebraic Curves

·Fixed a bug in computing adjoint linear systems for ordinary plane curves that would sometimes cause an illegal null sequence error. Reported by C. Quitte.

Analytic Jacobians

·An error could occur with certain inputs when the sign of the imaginary part of a complex number turned out to be zero. Reported by M. Stoll.

Coding Theory

·When running in secure mode, calls to BKLC no longer fail due to illegal use of GetEnv.

·The verbose output of CanteautChabaudsAttack could crash in some cases when displaying the statistics; this has now been fixed.

Commutative Algebra

·A bad case where PrimaryDecomposition was getting stuck has been fixed. Reported by S. Jambor.

·A problem in the projection map for quotients of affine algebras has been fixed. Reported by C. Quitte.

·A problem in the Image function for matrices over multivariate polynomials rings has been fixed. Reported by C. Quitte.

Elliptic Curves

·A possible crash in the computation of the Tamagawa number in the I* case where the elliptic curve has large coefficients has been fixed.

Finite Groups

·An error in the maximal subgroups of the classical group O+(8,q), q even, has been fixed. Previously a non-maximal subgroup had been included in the results returned by ClassicalMaximals. However, the results returned by MaximalSubgroups applied to an arbitrary finite group having O+(8,q) as a composition factor would have been correct. Bug found and fixed by D. Holt.

Global Arithmetic Fields

·A fix has been made to addition of orders.

·A problem in the sub constructor for orders in quadratic fields has been fixed. Illegal input to this function that does not define a suborder would cause internal errors. Reported by K. Brockhaus.

·Some fixes have been made to the computation of Galois groups.

L-Series

·A bug with eq was fixed. Reported by M. Stoll.

Local Fields

·Elements of general local fields now have the precision of their coefficients fixed so that there are no coefficients appearing with valuation greater than the absolute precision of the element any more than results from rounding.

·A fix has been made to a previous fix relating to the computation of the mapping of a local field into its ramified representation.

·A problem in the factorisation has been fixed that would cause runtime errors. This only affects the computation of Extensions. Reported by C. Greve.

·A problem in the computation of the unit group of local fields has been fixed. Reported by C. Greve.

Matrix Groups

·A problem when computing the image and kernel of a homomorphism with matrix group domain has been addressed. This caused the SolubleRadical function to hang, for instance.

·Code to set the order of a standard matrix group has been improved. Problem reported by E. O'Brien.

·Added WordInStrongGenerators for matrix groups. Request of E. O'Brien.

Polynomial Rings

·A crash in multivariate factorization over the integers has been fixed. Reported by S. Jambor.

Quaternion algebras

·pMatrixRing was ignoring the optional argument Precision in some cases. Reported by M. Masdeu.

System

·AddAttribute now returns an error message when attempting to add attributes to a type which may not have attributes. Reported by K. Andersen and others.

Toric Geometry

·Fixed a potential crash when creating a graded toric lattice.

·Corrected the result when taking the Cartesian product of a polytope with itself.