Recent work of Stein, Knapp, Koranyi and others has been concerned with nilpotent Lie groups which admit expanding automorphisms, that is, semisimple automorphisms whose eigenvalues are all greater than one in absolute value (cf.
No takes yet. Share an insight, caveat, or question.
Joan L. Dyer (1970) studied this question.
Synapse has enriched one closely related paper. Consider it for comparative context: