General transformation of alpha cluster model wave function to jj-coupling shell model in various 4N nuclei

The antisymmetrized quasi-cluster model (AQCM) is a method to describe a transition from the alpha-cluster wave function to the jj-coupling shell model wave function. In this model, the cluster-shell transition is characterized by only two parameters; R representing the distance between alpha clusters and Lambda describing the breaking of alpha clusters, and the contribution of the spin-orbit interaction, very important in the jj-coupling shell model, can be taken into account starting with the alpha cluster model wave function. In this article we show the generality of AQCM by extending the application to heavier region; various 4N nuclei from 4He to 52Fe. We show and compare the energy curves for the alpha+40Ca cluster configuration calculated with and without alpha breaking effect in 44Ti

Antisymmetrized molecular dynamics studies for exotic clustering phenomena in neutron-rich nuclei

We present a review of recent works on clustering phenomena in unstable nuclei studied by antisymmetrized molecular dynamics (AMD). The AMD studies in these decades have uncovered novel types of clustering phenomena brought about by the excess neutrons. Among them, this review focuses on the molecule-like structure of unstable nuclei. One of the earliest discussions on the clustering in unstable nuclei was made for neutron-rich Be and B isotopes. AMD calculations predicted that the ground state clustering is enhanced or reduced depending on the number of excess neutrons. Today, the experiments are confirming this prediction as the change of the proton radii. Behind this enhancement and reduction of the clustering, there are underlying shell effects called molecular- and atomic-orbits. These orbits form covalent and ionic bonding of the clusters analogous to the atomic molecules. It was found that this "molecular-orbit picture" reasonably explains the low-lying spectra of Be isotopes. The molecular-orbit picture is extended to other systems having parity asymmetric cluster cores and to the three cluster systems. O and Ne isotopes are the candidates of the former, while the $3\alpha$ linear chains in C isotopes are the latter. For both subjects, many intensive studies are now in progress. We also pay a special attention to the observables which are the fingerprint of the clustering. In particular, we focus on the monopole and dipole transitions which are recently regarded as good probe for the clustering. We discuss how they have and will reveal the exotic clustering.Comment: 96 pages, 44 figure

Systematic study for relation between nuclear structure and reaction in 10^{10}Be nucleus

We systematically investigate the relation between the nuclear structure and reaction in the $^{10}$Be nucleus using a theoretical framework. The structure of the $^{10}$Be nucleus is constructed with a cluster model based on a microscopic viewpoint. In this paper, the $^{10}$Be nucleus with different structures is prepared by manipulating the parameters of an effective nucleon-nucleon interaction. The nuclear structure and expectation values of physical quantities are drastically changed by the modification. We summarize such changes and show the effects on the elastic and inelastic scatterings for the proton and $^{12}$C targets in the microscopic coupled-channel calculation. Especially, we recently reported the visualization of dineutron correlation in $^{10}$Be on proton inelastic scattering in [Phys. Rev. C104, 034613 (2021)]. In this preceding work, we found that the changing the degree of dineutron correlation in $^{10}$Be leads to drastic changes of the inelastic cross section for the 2$_2^+$ state. The development (or breaking) of the dineutron correlation is governed by the strength of the spin-orbit interaction of the structure calculation. However, in the previous work, some of the realistic physical points were missing, for example, the binding energy. Therefore, we reconstruct the $^{10}$Be nucleus by adjusting the effective nucleon-nucleon interaction to obtain the reasonable binding energy of the ground state. With this improvement, we again discuss the dineutron correlation in the $^{10}$Be nucleus. We reconfirm the way to measure the degree of the development (or breaking) of dineutron cluster structure; the sensitivity to the inelastic cross section of the ground state to the 2$_2^+$ state of $^{10}$Be.Comment: 33 pages, 16 figures, 5 tables. arXiv admin note: text overlap with arXiv:2105.0302

Dineutron correlations in nuclear surface

Two-neutron correlation in quasi two-dimensional (2D) neutron matter is studied by means of the BCS theory to understand formation of nn pairs in nuclear surface of neutron-rich nuclei. The spin-zero nn pair correlation in low density neutron systems confined in an infinite slab is investigated in a simplified model that neutron motion of one direction is frozen. It is found that, when the slab is thin enough, the nn pairing gap enhances and the size shrinking of nn Cooper pair occurs at finite low-density region in the quasi-2D system

Honesty mediates the relationship between serotonin and reaction to unfairness

How does one deal with unfair behaviors? This subject has long been investigated by various disciplines including philosophy, psychology, economics, and biology. However, our reactions to unfairness differ from one individual to another. Experimental economics studies using the ultimatum game (UG), in which players must decide whether to accept or reject fair or unfair offers, have also shown that there are substantial individual differences in reaction to unfairness. However, little is known about psychological as well as neurobiological mechanisms of this observation. We combined a molecular imaging technique, an economics game, and a personality inventory to elucidate the neurobiological mechanism of heterogeneous reactions to unfairness. Contrary to the common belief that aggressive personalities (impulsivity or hostility) are related to the high rejection rate of unfair offers in UG, we found that individuals with apparently peaceful personalities (straightforwardness and trust) rejected more often and were engaged in personally costly forms of retaliation. Furthermore, individuals with a low level of serotonin transporters in the dorsal raphe nucleus (DRN) are honest and trustful, and thus cannot tolerate unfairness, being candid in expressing their frustrations. In other words, higher central serotonin transmission might allow us to behave adroitly and opportunistically, being good at playing games while pursuing self-interest. We provide unique neurobiological evidence to account for individual differences of reaction to unfairness