Luneburg-lens-like universal structural Pauli attraction in nucleus-nucleus interactions: origin of emergence of cluster structures and nuclear rainbows

TL;DR

This paper reveals that the Pauli exclusion principle induces a universal structural attraction between nuclei, explaining the emergence of cluster structures and nuclear rainbows through systematic studies of various nuclear systems.

Contribution

It demonstrates that the Pauli principle causes a universal structural attraction rather than repulsion, unifying the understanding of cluster formation and nuclear rainbows.

Findings

Pauli principle induces a universal structural attraction between nuclei.

Cluster structures emerge near threshold energies.

Nuclear rainbows result from this attraction at high energies.

Abstract

The Pauli exclusion principle plays an important role in many-body fermion systems preventing them from collapsing by repulsion. For example, the Pauli principle causes a repulsive potential at short distances between two $\alpha$ particles. On the other hand, the existence of nuclear rainbows demonstrates that the inter-nuclear potential is sufficiently attractive in the internal region to cause refraction. The two concepts of repulsion and attraction are seemingly irreconcilable. Contrary to traditional understanding, it is shown that the Pauli principle causes a {\it universal structural Pauli attraction} between nuclei rather than a {\it structural repulsive core}. Through systematic studies of $\alpha$+$\alpha$, $\alpha$+$^{16}$O, $\alpha$+$^{40}$Ca and $^{16}$O+$^{16}$O systems, it is shown that the emergence of cluster structures near the threshold energy at low energies and nuclear rainbows at high energies is a direct consequence of the Pauli principle.