Eur. Phys. J. B 60, 181-185 (2007)
https://doi.org/10.1140/epjb/e2007-00337-6

S-matrix poles close to thresholds in confined geometries

¹ Dipartimento di Fisica “G. Galilei”, Università di Padova, Via F. Marzolo 8, 35131 Padova, Italy
² Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Via F. Marzolo 8, 35131 Padova, Italy

Corresponding author: ^a giorgio.cattapan@pd.infn.it

Received: 25 June 2007
Revised: 23 October 2007
Published online: 8 December 2007

Abstract

We have studied the behavior of the S–matrix poles near threshold for quantum waveguides coupled to a cavity with a defect. We emphasize the occurrence of both dominant and shadow poles on the various sheets of the energy Riemann surface, and show that the changes of the total conductivity near threshold as the cavity's width changes can be explained in terms of dominant to shadow pole transitions.