The metric is that of a Cahen-Wallach symmetric space, whose coset
construction is reviewed in Section ..., with Aij = -
λ2δ
ij.
![1 2 1 2
[Pi,Mj ] = 4λ δijPv , [Pu, Pi] = Mi , [Pu,Mi ] = - 4λ Pi .](misprints45x.png)

should be changed to minus and the
parameter λ6 in the 1-form ω should be divided by the square root of 2:
