Symplectic structures and cohomologies on some solvmanifolds

We consider the question of existence of symplectic and Kahler structures on compact homogeneous spaces of solvable triangular Lie groups. The aim of the article is to clarify the situation with examples in this area. We prove that it is impossible to complete the construction of examples in the well-known article by Benson and Gordon on the structure of compact solvmanifolds with Kahler structure. We do this by proving the absence of lattices (and thereby a compact form) in the Lie groups of the above-mentioned article. We construct a new (similar) example for which, unlike the above examples, a compact form exists. We consider one class of solvable Lie groups, namely the class of almost abelian groups, and obtain for this class a characterization of those Lie groups for which the cohomologies of their compact solvmanifolds are isomorphic to the cohomologies of the corresponding Lie algebras. Until recently, such isomorphism has been known only for one specific class of Lie groups, namely the class of triangular groups. We give examples of new (almost abelian) Lie groups with such isomorphism.