Weak-mixing polygonal billiards
  We consider the set of polygons all of whose sides are vertical or horizontal with fixed combinatorics (for example all the figure "L"s). We show that there is a dense G $\delta$ subset of such polygons such that for each polygon in this G $\delta$ set the billiard flow is weakly-mixing in almost every direction. 
Alba M\'alaga Sabogal (UP11 UFR Sciences), Serge Troubetzkoy (I2M)
math.DS