η-Einstein Sasakian Lie algebras

Abstract

We study eta-Einstein Sasakian structures on Lie algebras, that is, Sasakian structures whose associated Ricci tensor satisfies an Einstein-like condition. We divide into the cases in which the Lie algebra’s centre is non-trivial (and necessarily one-dimensional) from those where it is zero. In the former case we show that any Sasakian structure on a unimodular Lie algebra is eta-Einstein. As for centreless Sasakian Lie algebras, we devise a complete characterisation under certain dimensional assumptions regarding the action of the Reeb vector. Using this result, together with the theory of normal j-algebras and modifications of Hermitian Lie algebras, we construct new examples of eta-Einstein Sasakian Lie algebras and solvmanifolds, and provide effective restrictions for their existence.