Classical r-matrices and Novikov algebras

Abstract: We study the existence problem for Novikov algebra structures on finite-dimensional Lie algebras. We show that a Lie algebra admitting a Novikov algebra is necessarily solvable. Conversely we present a $2$-step solvable Lie algebra without any Novikov structure. We use extensions and classical $r$-matrices to construct Novikov structures on certain classes of solvable Lie algebras.