Change log for Magma V2.21-5 (Released 2/7/2015)

Algebraic Number Fields

·An iterator has been provided to iterate through elements of quotients of orders of relative number fields by their ideals. Reported by M. Kirschmer.

·It is now possible to construct Random elements of quotients of orders of relative number fields by their ideals.

·Compatibility has been improved for orders of number fields. This allows the comparison of orders having the same coefficient ring using eq. Reported by M. Kirschmer.

Commutative Algebra

·A problem in comparison of module elements has been fixed. Reported by C. Quitte.

Dirichlet Characters

·A problem with assigning names to a Dirichlet group generators was fixed.

Elliptic Curves

·The MinimalQuadraticTwist intrinsic when applied to a rational whose numerator has a prime-power divisor pe with 6 | e and p > 3 congruent to 3 mod 4 could return a curve with a different j-invariant. Reported by A. Sutherland.

Groups

·A bug in Subgroups when using IndexEqual set to an impossible index has been fixed. Reported by A. Sutherland.

·A crash using the transversal map with groups of type GrpFPCox has been fixed. Reported by B. Howlett.

·If explicitly setting all of the conjugacy classes of a group, they are no longer re-ordered if they are already sorted. Previously, elements with the same order and length could be re-ordered in this case. Reported by S. Goldstein.

·A crash when computing preimages with a BlocksAction map has been fixed. Bug reported by Juergen Klueners.

Lattices

·Using the Max parameter with ShortestVectors could lead to incorrect caching of partial information, and give erroneous results for later enumerations. Reported by C. Doberstein.

Series Rings

·The IsSquare intrinsic for series over the rationals whose constant coefficient (after removing the valuation) was not 1 could give wrong answers due to Log/Exp not working. The same problem can also occur with IsPower more generally. Reported by M. Stoll.

·Roots, to a given precision, of polynomials over series rings over inexact rings have been disallowed.