Tooru Yoshida | Searcharxiv

arXiv2014

Nature of isomerism in exotic sulfur isotopes

We clarify the origin of the anomalously hindered $E2$ decay from the $4^+_1$ level in $^{44}$S by performing a novel many-body analysis in the shell model. Within a unified picture about the occurrence of isomerism in neutron-rich sulfur isotopes, the $4^+_1$ state is demonstrated to be a $K=4$ isomer dominated by the two-quasiparticle configuration $\nu\Omega^{\pi}=1/2^-\otimes\nu\Omega^{\pi}=7/2^-$. The $4^+_1$ state in $^{44}$S is a new type of high-$K$ isomer which has significant triaxiality.

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arXiv2012

New Generation of the Monte Carlo Shell Model for the K Computer Era

We present a newly enhanced version of the Monte Carlo Shell Model method by incorporating the conjugate gradient method and energy-variance extrapolation. This new method enables us to perform large-scale shell-model calculations that the direct diagonalization method cannot reach. This new generation framework of the MCSM provides us with a powerful tool to perform most-advanced large-scale shell-model calculations on current massively parallel computers such as the K computer. We discuss the validity of this method in ab initio calculations of light nuclei, and propose a new method to describe the intrinsic wave function in terms of the shell-model picture. We also apply this new MCSM to the study of neutron-rich Cr and Ni isotopes using the conventional shell-model calculations with an inert 40Ca core and discuss how the magicity of N = 28, 40, 50 remains or is broken.

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