**
Below is the ascii version of the abstract for 99-284.
The html version should be ready soon.**G. Panati, A. Teta
The Flux-Across-Surfaces Theorem for a Point Interaction Hamiltonian
(36K, LaTex)
ABSTRACT. The flux-across-surfaces theorem establishes a fundamental relation in
quantum scattering theory between the asymptotic outgoing state and a
quantity which is directly measured in experiments. We prove it for a
hamiltonian with a point interaction, using the explicit expression for
the propagator. The proof requires only assuptions on the initial state
and it covers also the case of zero-energy resonance. We also outline a
different approach based on generalized eigenfunctions, in view of a
possible extension of the result.