title: Pruning of orbits in four-disk and hyperbola billiards.
abstract: It is shown that for the four-disk system and the hyperbola billiard it is possible to construct a new symbolic plane preserving the orientation existing in the dynamical space. Physical orbits are mapped into the topological well-ordered plane and it is shown that the forbidden and allowed orbits are separated by a monotone pruning front.
authors.affiliation: Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen [large-closed-square], Denmark.
authors.forename: Kai T.
authors.initials: KT
authors.lastname: Hansen