STUDY OF DISSIPATION PROCESSES IN THE COLLECTIVE EXCITATIONS IN MANY-PARTICLE SYSTEMS

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(1) Model Study of the Dissipation in the Response FunctionResponse function of two-dimensional anharmonic oscillator was studied. The model allows a regular as well as chaotic properties depending on a single parameter. It was shown that the response shows generally a irregular pattern for a chaotic system, although there still remains a regular pattern which may be related to a persistent periodic orbit.(2) Study of the Fluctuation in the Giant Resonance StrengthsFluctuation properties of the strength function for giant quadrupole resonance in Calcium nuclei were studied based on the realistic Tamm-Dancoff calculation. Local scaling dimensions were calculated which suggests a possible doorway structure at a few MeV scale.(3) Collective Excitations in a Trapped Bose-Fermi Gas of AtomsTrapped alkali atomic gasses at a very low temperature is an example of a finite quantum many-body system, and shows a collective modes similar to giant resonances in nuclei. We considered a trapped Bose-Fermi mixed system and calculated static properties and collective excitations. We found that dipole out-of-phase oscillation of Bosons and Fermions becomes lower than the in-phase one, and also that the occurence of induced instability for a strong attractive Bose-Fermi interaction.(4) Related StudiesWe started some initial studies related to the present project which include : Feynman-Vernon influence functional approach to the decay of disoriented chiral condensates, study of the fluctuation of the strength functions in the random matrices, dissipation mechanism due to level crossings in the algebraic solvable model, etc.