Estimates of the Derivative of the Entropy of Gaussian Thermostats
  We consider a variation of an Anosov geodesic flow by Gaussian Thermostats and we obtain estimates of the derivative of the entropy map at the geodesic flow. In particular, we prove that the entropy of the geodesic flow is a local maximum for the entropy map. 
Alexander Arbieto and Adilson Lopes
math.DS