Continuum damping effects in nuclear collisions associated with twisted boundary conditions

Abstract

The time-dependent Skyrme Hartree-Fock calculations have been performed to study 24 Mg + 24 Mg collisions. The twisted boundary conditions, which can avoid finite box-size effects of the employed 3D coordinate space, have been implemented. The prolate deformed 24 Mg has been set to different orientations to study vibrations and rotations of the compound nucleus 48 Cr. Our time evolution results show continuum damping effects associated with the twist-averaged boundary condition play a persistent role after the fusion stage. In particular, a rotational damping in continuum is presented in calculations of both twist-averaged and absorbing boundary conditions, in which damping widths can be clearly extracted. It is unusual that the rotating compound nucleus in continuum evolves towards spherical but still has a considerable angular momentum.Introduction.-The real-time nuclear dynamics such as collective responses, large amplitude collisions and fissions have been studied extensively to probe effective interactions, many-body correlations and transport properties [1-3]. The basic theoretical framework for quantum many-body dynamics is the time-dependent Schrödinger equation with various approximations. In this respect, the microscopic time-dependent Hartree-Fock (TDHF) (or time-dependent density functional theory) was very successful for studies of nuclear dynamics, particularly the large amplitude dynamics [1-7]. The improved time-dependent-Hartree-Fock-Bogoliubov calculations have also been developed for superfluid systems, relying on tremendous computing capabilities [8,9]. Besides, the quantum molecular dynamics calculations have been widely used for heavy ion collisions at higher energies with two-body dissipations [10]. In the small amplitude limit of collective motions, TDHF results can match the random phase approximation (RPA), or linear resonance theory [2,11]. For nuclear collisions involving considerable excitation energies, the TDHF without pairing is a reasonable approximation. For too high excitation energies, the TDHF is not applicable when two-body collisions become prominent.

Fission of compound nuclei and the developments of microscopic fission theory

“…TD-HFB理论计算表明当采用不同有效核力时显示了相似 的强集体运动耗散的动力学行为 [53] , 在一定程度上验 效应可以考虑平均场以外的多体关联, 可以增加集体 自由度的波动而改善对碎片分布的描述 [52] . 目前国内 对TDHF的研究比较多 [57,58] , 但是TD-HFB由于计算量 过大而国内对这方面的研究还很缺乏.…”

An implementation of nuclear time-dependent density-functional theory and its application to the nuclear isovector electric dipole resonance

“…Recently, there have been efforts using more involved boundary conditions [36,37]. Based on these studies, we decide to use the ABC due to its simplicity and effectiveness.…”