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fix: computation of K1 over finite fields (#1557)
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thofma authored Jul 6, 2024
1 parent f8eabef commit 6b87cbe
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Showing 2 changed files with 14 additions and 1 deletion.
5 changes: 4 additions & 1 deletion src/AlgAssAbsOrd/LocallyFreeClassGroup.jl
Original file line number Diff line number Diff line change
Expand Up @@ -360,8 +360,11 @@ function _1_plus_j(A::StructureConstantAlgebra{<:FinFieldElem}, jacobson_radical
while !iszero(J)
J2 = J^2
Q, AtoQ = quo(J, J2)
absB = absolute_basis(base_ring(A)) # Generators of base ring as abelian group
for i = 1:dim(Q)
push!(onePlusJ, one(A) + AtoQ\Q[i])
for b in absB
push!(onePlusJ, one(A) + AtoQ\(b*Q[i]))
end
end
J = J2
end
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10 changes: 10 additions & 0 deletions test/AlgAssAbsOrd/LocallyFreeClassGroup.jl
Original file line number Diff line number Diff line change
Expand Up @@ -117,3 +117,13 @@ end
@test is_isomorphic(kernel_group(ZG), abelian_group(o))[1]
end
end

let
A, = StructureConstantAlgebra(group_algebra(GF(2, 3), small_group(2, 1)))
u = Hecke.K1(A; do_units = true)
@test length(closure(u, *)) == 8 * 7

A, = StructureConstantAlgebra(group_algebra(GF(2, 4), small_group(2, 1)))
u = Hecke.K1(A; do_units = true)
@test length(closure(u, *)) == 16 * 15
end

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