Periodic orbit bifurcations and local symmetry restorations in exotic-shape nuclear mean fields

TL;DR

This paper explores how local symmetries and periodic-orbit bifurcations influence shell effects in exotic nuclear shapes, highlighting the role of classical-quantum correspondence in shape-dependent shell structure enhancements.

Contribution

It reveals the significance of local dynamical symmetries and bifurcations in the emergence of exotic shell structures in nuclear mean fields with tetrahedral and octupole deformations.

Findings

Shell effects are enhanced at Y32 tetrahedral deformation.

Shape parametrizations connecting sphere and tetrahedron show stronger shell effects.

Local symmetries from bifurcations are crucial for exotic shell structures.

Abstract

The semiclassical origins of the enhancement of shell effects in exotic-shape mean-field potentials are investigated by focusing attention on the roles of the local symmetries associated with the periodic-orbit bifurcations. The deformed shell structures for four types of pure octupole shapes in the nuclear mean-field model having a realistic radial dependence are analyzed. Remarkable shell effects are shown for a large Y32 deformation having tetrahedral symmetry. Much stronger shell effects found in the shape parametrization smoothly connecting the sphere and the tetrahedron are investigated from the view point of the classical-quantum correspondence. The local dynamical symmetries associated with the bridge orbit bifurcations are shown to have significant roles in emergence of the exotic deformed shell structures for certain combinations of the surface diffuseness and the tetrahedral deformation parameters.