| Résume | In 1986, Gesztesy et al. revealed the surprising behavior of thresholds
resonances for two-dimensional scattering systems: their contributions
to Levinson's theorem are either 0 or 1, but not 1/2 as previously known
for systems in dimension 1 and 3. During this seminar, we shall review
this result, and explain how a C*-algebraic framework leads to a better
understanding of this surprise. The main algebraic tool consists of a
hexagonal algebra of Cordes, replacing a square algebra sufficient for
systems in 1D and 3D. No prior knowledge on scattering theory is
expected from the audience. This presentation is based on a joint work
with A. Alexander, T.D. Nguyen, and A. Rennie. |
