**
Below is the ascii version of the abstract for 06-261.
The html version should be ready soon.**Christian Gerard, Rafael Tiedra de Aldecoa
Generalized definition of time delay in scattering theory
(251K, Postscript)
ABSTRACT. We advocate for the systematic use of a symmetrized definition of time delay in scattering
theory. In two-body scattering processes, we show that the symmetrized time delay exists for
arbitrary dilated spatial regions symmetric with respect to the origin. It is equal to the usual
time delay plus a new contribution, which vanishes in the case of spherical spatial regions. We
also prove that the symmetrized time delay is invariant under an appropriate mapping of time
reversal. These results are also discussed in the context of classical scattering theory.