  We construct Birkhoff cones for dispersing billiards, which are contracted by
the action of the transfer operator. This construction permits the study of
statistical properties not only of regular dispersing billiards but also of
sequential billiards (the billiard changes at each collision in a prescribed
manner), open billiards (the dynamics exits some region or dies when hitting
some obstacle) and many other examples. In particular, we include applications
to chaotic scattering and the random Lorentz gas.
