|Revista Colombiana de Matemáticas|
Abstract. We prove that 2 is a Lewowicz number of every linear Anosov diffeomorphism on the torus. This result is independent of any linear metric and provides an explicit Lyapounov function for the diffeomorphisms.Palabras claves. Manifold, Riemannian manifold, Anosov diffeomorphism, quadratic form, positive definite quadratic form.