EXACT AND QUASI-CLASSICAL FREDHOLM SOLUTIONS OF QUANTUM BILLIARDS

Quantum billiards are much studied as perhaps the simplest case which presents the central difficulty that the quasiclassical approximation is expressed as a divergent series. We find here, using the Fredholm method, an exact Green's function for billiards expressed as a ratio of absolutely convergent series. We make the quasiclassical approximation to this ratio. The method provides a convergence argument for previous results and an extension of results obtained for the spectrum to the full Green's function. © 1995 The American Physical Society.