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arXiv · 2607.11453

Search for the Double Poles of the Scattering Matrix in Light Nuclei

David Cardona Ochoa·Marek Płoszajczak·Nicolas Michel
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Abstract

Exceptional points (EPs) are non-Hermitian degeneracies at which two eigenvalues and their eigenvectors coalesce, producing a defective Hamiltonian and a double pole of the $S$-matrix. Using the coupled-channel Gamow Shell Model with the $\ell=1$ spin-orbit strengths as control parameters, we locate and characterize EPs in $^6\text{Li}$, $^7\text{Li}$, $^7\text{Be}$, and $^8\text{Be}$, and analyze their imprint on energies, widths, phase rigidity, spectroscopic factors, elastic cross sections, survival probabilities, and spectral functions. The signatures of the EP in scattering and time-domain observables are found to be strongly channel-dependent, and threshold effects play a decisive role in determining the accessibility of the EP in parameter space.

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David Cardona Ochoa, Marek Płoszajczak, Nicolas Michel. 2026-07-13. Search for the Double Poles of the Scattering Matrix in Light Nuclei. https://doi.org/10.1103/ykjr-796z

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