Three-dimensional Lorentzian homogeneous Ricci solitons (Q1760338)

This paper presents an elegant study of three-dimensional Lorentzian homogeneous Ricci solitons. The authors prove that the Lorentzian signature allows the existence of expanding, steady, and shrinking left-invariant Ricci solitons. For all non-trivial examples the Ricci operator is not diagonalizable and has three equal eigenvalues.