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.