Theory of Low Mass Stars and Brown Dwarfs: Success and Remaining Uncertainties

École Normale Supérieure de Lyon, CRAL, 46 allée d'Italie, 69364 Lyon, France

Abstract

Important progress has been made within the past few years regarding the theory of low mass stars (m < 1 M_⊙) and brown dwarfs (m < 0.075 M_⊙). The main improvements concern the equation of state of dense plasmas and the modelling of cool and dense atmospheres, necessary for a correct description of such objects. These theoretical efforts now yield a better understanding of these objects and good agreement with observations regarding colour-magnitude diagrams of globular clusters, mass-magnitude relationships and near-IR colour-magnitude diagrams for open clusters. However uncertainties still remain regarding synthetic optical colours and the complex problem of dust formation in the coolest atmosphere models. We will present a review of the current success and uncertainties of the theory of these objects, which may guide forthcoming projects with GAIA.