The entropy of 'strange' billiards inside n-simplexes
  In the present work we investigate a new type of billiards defined inside n-simplex regions. We determine an invariant ergodic (SRB) measure of the dynamics for any dimension. In using symbolic dynamics the (KS or metric) entropy is computed and we find that the system is chaotic for all cases n > 2. 
Thomas Sch\"urmann and Ingo Hoffmann