arXiv subjects

David Cardona Ochoa

Publications and source records attributed to David Cardona Ochoa.

3 recordsLinked to original sources

arXiv2026

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

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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arXiv2026

Double pole $S$-matrix singularity in the continuum of $^7$Be

The double pole singularity of the $S$-matrix, the so-called exceptional point, associated with the $5/2^-$ doublet of resonances in the spectrum of $^{7}$Be has been identified in the framework of the Gamow shell model. The exceptional point singularity is demonstrated by the coalescence of wave functions and spectral functions of the two resonances, as well as by the singular behavior of spectroscopic factors and electromagnetic transitions.

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arXiv2025

Gamow shell model description of exceptional point in $^7$Li

We report the first identification of an exceptional point (EP) within the Gamow Shell Model in the Coupled Channels representation (GSM-CC). In the spectrum of $^{7}$Li, an EP is found for the $5/2^-$ doublet, where the two states coalesce in both energy and width, the phase rigidity vanishes, and the S-matrix develops a double pole. These features manifest directly in observables: the elastic cross section acquires a split-peak structure, and the phase shift shows a single $2π$ jump. This work demonstrates that GSM-CC provides a powerful framework to explore EP phenomena in nuclei and their experimental signatures.

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