arXiv subjects

Lu Guo

Publications and source records attributed to Lu Guo.

42 records · Page 3Linked to original sources

arXiv2007

Boost-invariant mean field approximation and the nuclear Landau-Zener effect

We investigate the relation between time-dependent Hartree-Fock (TDHF) states and the adiabatic eigenstates by constructing a boost-invariant single-particle Hamiltonian. The method is numerically realized within a full three-dimensional TDHF which includes all the terms of the Skyrme energy functional and without any symmetry restrictions. The study of a free translational motion of a nucleus demonstrates the validity of the concept of boost-invariant and adiabatic TDHF states. The interpretation is further corroborated by the test case of fusion of $^{16}{\textrm O}$+$^{16}{\textrm O}$. As a first application, we present a study of the nuclear Landau-Zener effect on a collision of $^{4}{\textrm {He}}$+$^{16}{\textrm O}$.

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arXiv2007

Nuclear Giant Resonances and Linear Response

We search for nonlinear effects in nuclear giant resonances (GRs), in particular the isovector dipole and the isoscalar quadrupole modes. To that end, we employ a spectral analysis of time-dependent Hartree-Fock (TDHF) dynamics using Skyrme forces. Based on TDHF calculations over a wide range of excitation amplitudes, we explore the collectivity and degree of harmonic motion in these modes. Both GR modes turn out to be highly harmonic in heavy nuclei from A=100 on. There is no trace of a transition to irregular motion and multiple resonances are predicted. Slight anharmonicities are seen for light nuclei, particularly for $^{16}$O. These are mainly caused by the spin-orbit splitting.

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arXiv2007

To what extent does the self-consistent mean-field exist?

A non-convergent difficulty near level-repulsive region is discussed within the self-consistent mean-field theory. It is shown by numerical and analytic studies that the mean-field is not realized in the many-fermion system when quantum fluctuations coming from two-body residual interaction and quadrupole deformation are larger than an energy difference between two avoided crossing orbits. An analytic condition indicating a limitation of the mean-field concept is derived for the first time.

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arXiv2005

Applicability of self-consistent mean-field theory

Within the constrained Hartree-Fock (CHF) theory, an analytic condition is derived to estimate whether a concept of the self-consistent mean field is realized or not in level repulsive region. The derived condition states that an iterative calculation of CHF equation does not converge when the quantum fluctuations coming from two-body residual interaction and quadrupole deformation become larger than a single-particle energy difference between two avoided crossing orbits. By means of the numerical calculation, it is shown that the analytic condition works well for a realistic case.

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arXiv2005

Rotational damping in a multi-$j$ shell particles-rotor model

The damping of collective rotational motion is investigated by means of particles-rotor model in which the angular momentum coupling is treated exactly and the valence nucleons are in a multi-$j$ shell mean-field. It is found that the onset energy of rotational damping is around 1.1 MeV above yrast line, and the number of states which form rotational band structure is thus limited. The number of calculated rotational bands around 30 at a given angular momentum agrees qualitatively with experimental data. The onset of rotational damping takes place gradually as a function of excitation energy. It is shown that the pairing correlation between valence nucleons has a significant effect on the appearance of rotational damping.

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arXiv2004

Characteristic Feature of Self-Consistent Mean-Field in Level Crossing Region

A shape change of the self-consistent mean-field induced by a configuration change is discussed within the conventional constrained Hartree-Fock (CHF) theory. It is stressed that a single-particle level crossing dynamics should be treated carefully, because the shape of the mean-field in such a finite many-body system as the nucleus strongly changes depending on its configuration. This situation is clearly shown by applying an adiabatic assumption, where the most energetically favorable single-particle states are assumed to be occupied. The excited HF states and the continuously-connected potential energy curves are given by applying the configuration dictated CHF method. The effect of pairing correlation is discussed in the level crossing region. Triaxial deformed results in our Hartree-Fock-Bogoliubov (HFB) calculation with Gogny force nicely reproduce the available experimental data of Ge isotopes. From our numerical calculation, it is concluded that the CHFB state is more fragile than the CHF state in the level crossing region.

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