Harmonic tensors on three-dimensional Lie groups with left-invariant Lorentz metric (Q1048563)

Let \(G\) be a Lie group and \(S\) be the Schouten--Weil tensor. The authors define an antisymmetric \(2\)-tensor \(W\) from \(S\), and they classify the three-dimensional unimodular Lie groups \(G\) (via their corresponding Lie algebras) with left-invariant Lorentz metric, for which the tensor \(W\) is harmonic.