The work consists of two introductory courses, developing different
points of view on the study of the asymptotic behaviour of the geodesic
flow, namely: the probabilistic approach via martingales and mixing (by
Stéphane Le Borgne); the semi-classical approach, by operator theory and
resonances (by Frédéric Faure and Masato Tsujii). The contributions aim
to give a self-contained introduction to the ideas behind the three
different approaches to the investigation of hyperbolic dynamics. The
first contribution focus on the convergence towards a Gaussian law of
suitably normalized ergodic sums (Central Limit Theorem). The second one
deals with Transfer Operators and the structure of their spectrum
(Ruelle-Pollicott resonances), explaining the relation with the
asymptotics of time correlation function and the periodic orbits of the
dynamics.