--- title: "Magma V2.15-4 Patch Notes" canonical: "https://docs.magma-maths.org/patchnotes/2.15-4.html" source: "https://docs.magma-maths.org/patchnotes/2.15-4.md" --- # Magma V2.15-4 Patch Notes ## Algebraic Curves - `IsNodal` checks for plane curves have been corrected to work for (geometrically) non-reduced curves. Bug reported by A. Brumer. - The `Genus` crash over finite fields has been fixed (see note in the Matrices section above). ## Arithmetic Geometry - A bug with EisensteinProjection of a modular form that was already in an EisensteinSubspace has been fixed. ## Commutative Algebra - A crash in primary decomposition of positive dimensional ideals has been fixed. - A hang in Groebner basis computation for ideals over GF(2) with a large number of variables has been fixed. Reported by J. Erickson. ## Galois Groups - The computation of Galois Groups over function fields of positive characteristic has been switched off due to too many problems. A rewrite is in progress. ## Group Representations - When dealing with a natural permutation module of a permutation group, the map returned by the `Representation` function now uses methods equivalent to using [`PermutationMatrix`](../MatricesLinearAlgebra/Matrices/creation.md#function-permutationmatrix-rng-rngintelt) rather than using generic group homomorphism methods. Suggested by Markus Grassl. ## Groups - A trap for large cyclic components has been installed in the `FPGroup` function for groups of type `GrpAb`. Reported by Eamonn O’Brien. - A crash which occurred when constructing the maximal subgroups of L(10, 2) has been fixed. Reported by Colva Roney-Dougal. - A bug in filtering subgroups produced by the `Subgroups` function when the new method for expanding maximal subgroups is used has been fixed. Bug reported by Florian Moeller. ## Matrices - A bug involving matrices of polynomials over finite fields (coming out of calls to `Genus`) has been fixed. Reported by A. Brumer.