Interfering resonances in a quantum billiard

We present a method for numerically obtaining the positions, widths, and wa ve functions of resonance states in a two-dimensional billiard connected to a waveguide. For a rectangular billiard, we study the dynamics of three re sonance poles lying separated from the other ones. As a function of increas ing coupling strength between the waveguide and the billiard two of the sta tes become trapped while the width of the third one continues to increase f or all coupling strengths. This behavior of the resonance poles is reflecte d in the time delay function, which can be studied experimentally. [S1063-6 51X(98)14112-0].