Infinitely many periodic orbits of exact magnetic flows on surfaces for   almost every subcritical energy level
  We consider an exact magnetic flow on the tangent bundle of a closed surface. We prove that for almost every energy level $\kappa$ below the Ma\~n\'e critical value of the universal cover there are infinitely many periodic orbits with energy $\kappa$. 
Alberto Abbondandolo, Leonardo Macarini, Marco Mazzucchelli, Gabriel   P. Paternain
math.DS math.SG