ABSTRACT
Scattering theory deals with the evolution of states of a system and, in particular, attempts to relate the state of a system as t → +∞ with the state of that system as t → −∞. In Chapter 3 we indicated that such a comparison could be made in terms of so-called wave operators. In this chapter we shall introduce these quantities rather more properly and outline some of their more important properties. This we can do most conveniently in an abstract setting; we shall consider specific cases later.
