THE EXCITATION OF A QUANTUM GAS OF INDEPENDENT FERMIONS IN A DEFORMING CAVITY - PERIODICITY OF DRIVING VS. LANDAU-ZENER TRANSITIONS

The numerically calculated excitation of a quantum gas of 112 non-inte racting fermions in a hard-walled cavity changing its shape is analyse d for one and for half of the oscillation cycle. Spheroidal and Legend re polynomid distortions, P-2, P-1, P-4, P-5 and P-6 around the sphere and the octupole deformed shape are considered. Oscillations of the e xcitation energy as a function of the driving frequency, especially pr onounced for low frequencies, are related to quantum interference betw een Landau-Zener transitions at successively traversed avoided crossin gs, This irregular component of excitation may be linked to the period icity of the driving motion since it is strongly suppressed for one-ha lf of the oscillation period. It is argued that the wall formula descr ibes quantum one-body dissipation in aperiodic processes better than i n periodic ones. (C) 1997 Elsevier Science B.V.