Stability of Anosov Diffeomorphisms

Definition 1. Let < , > be a C∞ Riemannian metric on M and | · | its induced norm on TxM for each x ∈ M . We say that f ∈ D is Anosov if 1. the tangent bundle of M splits in a Whitney direct sum of continuous subbundles TM = E ⊕ E, where E and E are Df -invariant, 2. there exists constants c, c′ > 0 and 0 < λ < 1 such that |Dfn xv| < c λn|v| |Df−n x w| < c′ λn|w| for all x ∈ M , v ∈ E x, and w ∈ E x and n > 0. M being compact, this definition is independent of the Riemannian metric < , >. Also, E and E are uniquely determined by the above conditions.