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change IsomorphismPermGroupForMatrixGroup#6244

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ThomasBreuer wants to merge 1 commit intogap-system:masterfrom
ThomasBreuer:TB_IsomorphismPermGroupForMatrixGroup
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change IsomorphismPermGroupForMatrixGroup#6244
ThomasBreuer wants to merge 1 commit intogap-system:masterfrom
ThomasBreuer:TB_IsomorphismPermGroupForMatrixGroup

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Use a known NiceMonomorphism also in the case that its image is not a permutation group.

The idea is:
We trust GAP that the image is nicer than the given group, in the sense that computing an IsomorphismPermGroup for the image is easier.
An example is that the given group is a matrix group in characteristic zero and its NiceMonomorphism is a reduction to a matrix group over a finite field.

(This strategy works only because NiceMonomorphism guarantees an image that is really nicer.
Note that other functions do not have this property, for example SmallerDegreePermutationRepresentation is allowed to return an identity mapping.)

(The same change has been implemented in oscar-system/Oscar.jl/pull/5791.)

Use a known `NiceMonomorphism` also in the case that its image
is *not* a permutation group.

The idea is:
We trust GAP that the image is nicer than the given group,
in the sense that computing an `IsomorphismPermGroup` for the image
is easier.
An example is that the given group is a matrix group in characteristic
zero and its `NiceMonomorphism` is a reduction to a matrix group
over a finite field.

(This strategy works only because `NiceMonomorphism` guarantees
an image that is really nicer.
Note that other functions do not have this property,
for example `SmallerDegreePermutationRepresentation` is allowed
to return an identity mapping.)
@ThomasBreuer ThomasBreuer added kind: enhancement Label for issues suggesting enhancements; and for pull requests implementing enhancements topic: library release notes: not needed PRs introducing changes that are wholly irrelevant to the release notes labels Feb 23, 2026
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