Special linear group of finite ring is finite?

[Liam Baker]

Hello there!

I am trying to do some computations with the special linear group of a finite ring (given as the quotient ring of a larger ring), and am running into an issue in which it seems that Sagemath doesn't know that the special linear group of a finite ring is finite? Here is a minimal working example which reproduces the error:

q = 7 FqT.<T> = GF(q)[] N = T^2+1 FqTN = QuotientRing(FqT, N*FqT) S = SL(2,FqTN) S.is_finite()This error arose when I was trying to enumerate subgroups of this special linear group. But the method I found in the Sagemath documentation, conjugacy_classes_subgroups(), seems to not exist for a special linear group?

[Vincent Delecroix]

Indeed, the problem comes from two methods calling each other

* S.order (inherited from sage/groups/group.pyx)
* S.cardinality (inherited from sage/categories/finite_groups.py)

I filled a bug report https://github.com/sagemath/sage/issues/35490

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