ROLE OF THE EDGE ORBITS IN THE SEMICLASSICAL QUANTIZATION OF THE STADIUM BILLIARD

In the periodic orbit quantization of the stadium billiard, we show that important contributions may be due to the edge orbits, i.e. to orbits bouncing between points where the curvature of the boundary is discontinuous. We explicitly show that these edge orbits are necessary to reproduce several amplitudes of the length spectrum defined by the Fourier transform of the staircase function. In this way, we explain some features, overlooked in recent experiments on microwave cavities.