S-expansions of three-dimensional Lie algebras
  S-expansions of three-dimensional real Lie algebras are considered. It is shown that the expansion operation allows one to obtain a non-unimodular Lie algebra from a unimodular one. Nevertheless S-expansions define no ordering on the variety of Lie algebras of a fixed dimension. 
Maryna Nesterenko
math-ph math.MP math.RA