Quantitative recurrence for free semigroup actions
  We consider finitely generated free semigroup actions on a compact metric space and obtain quantitative information on Poincar\'e recurrence, average first return time and hitting frequency for the random orbits induced by the semigroup action. Besides, we relate the recurrence to balls with the rates of expansion of the semigroup's generators and the topological entropy of the semigroup action. Finally, we establish a partial variational principle and prove an ergodic optimization for this kind of dynamical action. 
Maria Carvalho, Fagner B. Rodrigues, and Paulo Varandas
math.DS math-ph math.MP