A. Delshams, R. de la Llave, T. M. Seara
A geometric approach to the existence of orbits with 
unbounded energy in generic periodic perturbations 
by a potential of 
generic geodesic flows of ${\bf T} ^{2}$
(263K, latex)

ABSTRACT.  We give a proof based in geometric perturbation theory of a result 
proved by J.N.~Mather using variational methods. 
Namely, the existence of orbits with unbounded energy in 
perturbations of a generic geodesic flows in ${\bf T}^2$ 
by a generic periodic potential.