Description
An arrangement is said to be decomposable if the derived subalgebra of its holonomy Lie algebra is a direct sum of the derived subalgebras of free Lie algebras, indexed by the rank-2
flats of the arrangement. At the time of writing, it is not known if the answer depends on the characteristic of the coefficient ring.
i1 : X3 = arrangement "X3"
o1 = {x , x , x , x + x , x + x , x + x }
1 2 3 1 2 1 3 2 3
o1 : Hyperplane Arrangement
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i2 : isDecomposable X3
o2 = true
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i3 : isDecomposable(X3,ZZ/5)
o3 = true
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i4 : isDecomposable typeA(3)
o4 = false
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