Complex structures having nilpotent and solvable eigenspaces

Author(s)

Edson Carlos Licurgo Santos

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Matemática, Estatística e Computação Científica
• Defense date: 2007-06-25

Examining board members

Luiz Antonio Barrera San Martin; Pedro Jose Catuogno; Caio José Colletti Negreiros; Maria Laura Barberis; Esmerindo de Sousa Bernardes

• Advisor: Luiz Antonio Barrera San Martin

Abstract

Let (g; [·,·]) be a Lie algebra with an integrable complex structure J. The ±i eigenspaces of J are complex subalgebras of gC isomorphic to the algebra (g; [*]J )with bracket [X * Y ]J = ½ ([X, Y ] - [JX, JY ]). We consider, in chapter three, thecase where these subalgebras are nilpotent and prove that the original Lie algebra(g, [·,·]) must be solvable. We consider also the 6-dimensional case and determineexplicitly the possible nilpotent Lie algebras (g; [*]J ). We finish this chapter byproducing several examples illustrating different situations, in particular we showthat for each given s there exists g with complex structure J such that (g; [*]J ) iss-step nilpotent. Similar examples of hypercomplex structures are also built.In Chapter 3 we consider the case where the ± i eigenspaces of J are solvablecomplex subalgebras and gC is a semisimple Lie algebra. We prove that, if g is compact, such a complex structure comes from a subspace of the Cartan subalgebra.We finish this chapter by considering the case where the solvable complex subalgebras are contained in Borel subalgebras of an open orbit of the action of inner automorphisms of the real algebra.At the end of the thesis we present an algorithm, made in MAPLE, that allowus to verify the Jacobi identity when the Lie brackets are defined by the structureconstants (AU)