Lower and upper bounds for the Lyapunov exponents of twisting dynamics:   a relationship between the exponents and the angle of the Oseledet's   splitting
  We consider locally minimizing measures for the conservative twist maps of the $d$-dimensional annulus or for the Tonelli Hamiltonian flows defined on a cotangent bundle $T^*M$. For weakly hyperbolic such measures (i.e. measures with no zero Lyapunov exponents), we prove that the mean distance/angle between the stable and the unstable Oseledet's bundles gives an upper bound of the sum of the positive Lyapunov exponents and a lower bound of the smallest positive Lyapunov exponent. Some more precise results are proved too. 
Marie-Claude Arnaud (LANLG)
math.DS