Author: Peter Bubenik Title: Separated Lie models and the homotopy Lie algebra Author's e-mail address: p.bubenik@csuohio.edu AMS classification number: Primary 55P62; Secondary 17B55 arXiv submission number: math.AT/0406405 to appear in the Journal of Pure and Applied Algebra Abstract: The homotopy Lie algebra of a simply connected topological space, X, is given by the rational homotopy groups on the loop space of X. Following Quillen, there is a connected differential graded free Lie algebra (dgL) called a Lie model, which determines the rational homotopy type of X, and whose homology is isomorphic to the homotopy Lie algebra. We show that such a Lie model can be replaced with one that has a special property we call separated. The homology of a separated dgL has a particular form which lends itself to calculations. We give connections to the radical of the homotopy Lie algebra and the Avramov-Felix conjecture. Examples that are worked out in detail include wedges of spheres on any "thickness" and connected sums of products of spheres.