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Physical Review C

Nonlinear resonance in the time-dependent Hartree-Fock manifold

Fumihiko Sakata, T. Kubo, Toshio Marumori, K. Iwasawa, Yukio Hashimoto

Published Jul 1, 1994• 5 citations

Abstract

In order to try to open a new scope to explore the mutual dependence between the single-particle and collective modes of motion near to the level crossing region, a general method is developed to investigate the nonlinear resonant structure of the time-dependent Hartree-Fock (TDHF) manifold, without depending on the adiabatic assumption. By using the Lie canonical transformation method with the Deprit perturbation treatment, in this method, the maximal integrable-form representation of the TDHF manifold is introduced. This representation plays an essential role in exploring the nonlinear resonant structure of the TDHF manifold, which characterizes complex topology of the manifold. Aiming at relating the nonlinear resonance in the TDHF manifold with the dynamics between the single-particle and collective modes of motion near to the level crossing region, structure of the TDHF wave function in the nonlinear resonant region is investigated. It is clarified that an isolated nonlinear resonant region of the TDHF manifold is characterized by a local constant of motion (dynamical symmetry) and generates a new type of dynamical stable single-Slater-determinant states, which is topologically different from the TDHF states near the HF ground state, and cannot be reached by the conventional static Hartree-Fock method, constrained Hartree-Fock method, nor the adiabatic TDHF theories. One may expect that the appearance mechanism of the new dynamical stable single-Slater-determinant states gives us a new scope for understanding occurrence mechanism of a variety of collective sideband structure near to the level crossing region.

DOI: 10.1103/physrevc.50.138

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By applying the microscopic theory of dynamical collective submanifold, which has been formulated by the present authors, to a system with a simple model Hamiltonian, characteristic features of large-amplitude motion described by the time-dependent Hartree-Fock (TDHF) theory are visualized. Our theory dynamically defines an “optimum” submanifold out of the TDHF symplectic manifold (phase space) in such a way that the Hamiltonian on the submanifold is stationary with respect to variations perpendicular to it. The theory also classifies the submanifold into three different regions in terms of stablility and separability conditions. It is displayed that these three regions characterize collective, dissipative and stochastic motions in the TDHF theory.

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To visualize complex structure of the excited states in the many-fermion system, a profile function of the eigenstate within the quantum phase space is defined by using the boson expansion theory. When the anharmonic interaction is sufficiently weak where a corresponding semi-quantum system described by the time-dependent Hartree-Fock (TDHF) theory shows isolated resonant structure, there exists a remarkable similarity between the Poincaré section map of the TDHF trajectories and the profile functions of the eigenstates. It is shown that these eigenstates are well understood by using a new concept of quantum nonlinear resonance. It is also shown that a pair of newly appeared states due to the quantum resonance is not associated with any dissolution in a number of the good quantum numbers.

Aiming at exploring microscopic dynamics responsible for the dissipative large-amplitude collective motion, the dynamic response and correlation functions are introduced within the general theory of nuclear coupled-master equations. The theory is based on the microscopic theory of nuclear collective dynamics which has been developed within the time-dependent Hartree-Fock (TDHF) theory for disclosing the complex structure of the TDHF manifold. A systematic numerical method for calculating the dynamic response and correlation functions is proposed. By performing numerical calculation for a simple model Hamiltonian, it is pointed out that the dynamic response function gives important information in understanding the large-amplitude dissipative collective motion which is described by an ensemble of trajectories within the TDHF manifold.