The theory of Lie algebras and algebraic groups has been an area of active research in the last 50 years. It intervenes in many different areas of mathematics: for example invariant theory, Poisson geometry, harmonic analysis, mathematical physics. The aim of this book is to assemble in a single volume the algebraic aspects of the theory so as to present the foundation of the theory in characteristic zero. Detailed proofs are included and some recent results are discussed in the last chapters. All the prerequisites on commutative algebra and algebraic geometry are included.

Résumé
The theory of groups and Lie algebras is interesting for many reasons. In the mathematical viewpoint, it employs at the same time algebra, analysis and geometry. On the other hand, it intervenes in other areas of science, in particularindi?erentbranchesofphysicsandchemistry.Itisanactivedomain of current research. Oneofthedi?cultiesthatgraduatestudentsormathematiciansinterested in the theory come across, is the fact that the theory has very much advanced, andconsequently,theyneedtoreadavastamountofbooksandarticlesbefore they could tackle interesting problems. One of the goals we wish to achieve with this book is to assemble in a single volume the basis of the algebraic aspects of the theory of groups and Lie algebras. More precisely, we have presented the foundation of the study of ?nite-dimensional Lie algebras over an algebraically closed ?eld of characteristic zero. Here, the geometrical aspect is fundamental, and consequently, we need to use the notion of algebraic groups. One of the main di?erences between this book and many other books on the subject is that we give complete proofs for the relationships between algebraic groups and Lie algebras, instead of admitting them. We have also given the proofs of certain results on commutative al- bra and algebraic geometry that we needed so as to make this book as se- contained as possible. We believe that in this way, the book can be useful for both graduate students and mathematicians working in this area. Let us give a brief description of the material treated in this book.

Contenu
Results on topological spaces.- Rings and modules.- Integral extensions.- Factorial rings.- Field extensions.- Finitely generated algebras.- Gradings and filtrations.- Inductive limits.- Sheaves of functions.- Jordan decomposition and some basic results on groups.- Algebraic sets.- Prevarieties and varieties.- Projective varieties.- Dimension.- Morphisms and dimension.- Tangent spaces.- Normal varieties.- Root systems.- Lie algebras.- Semisimple and reductive Lie algebras.- Algebraic groups.- Affine algebraic groups.- Lie algebra of an algebraic group.- Correspondence between groups and Lie algebras.- Homogeneous spaces and quotients.- Solvable groups.- Reductive groups.- Borel subgroups, parabolic subgroups, Cartan subgroups.- Cartan subalgebras, Borel subalgebras and parabolic subalgebras.- Representations of semisimple Lie algebras.- Symmetric invariants.- S-triples.- Polarizations.- Results on orbits.- Centralizers.- ?-root systems.- Symmetric Lie algebras.- Semisimple symmetric Lie algebras.- Sheets of Lie algebras.- Index and linear forms.