arXiv subjects

Kévin Fossez

Publications and source records attributed to Kévin Fossez.

3 recordsLinked to original sources

arXiv2026

What is a resonance? And why does it matter?

The resonance phenomenon is of central importance in many areas of physics, with particular significance in the study of nuclear structure and reactions. Starting from the classical framework of damped driven oscillations, this text introduces and analyzes quantum-mechanical resonances in a pedagogical and systematic fashion, with emphasis on applications in nuclear physics. Building on the formal theory of resonances, the text elucidates the relationship between experimental observations, phenomenological insights, and computational methods used to characterize and describe resonant states. The discussion encompasses the diverse manifestations of nuclear resonances, ranging from few- to many-body systems, all the way to collective phenomena and to exotic systems that appear near the limits of nuclear stability. References to the relevant literature are provided to assist readers who wish to explore specific topics in more depth.

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arXiv2025

Towards scalable bound-to-resonance extrapolations for few- and many-body systems

In open quantum many-body systems, the theoretical description of resonant states of many particles strongly coupled to the continuum can be challenging. Such states are commonplace in, for example, exotic nuclei and hadrons, and can reveal important information about the underlying forces at play in these systems. In this work, we demonstrate that the complex-augmented eigenvector continuation (CA-EC) method, originally formulated for the two-body problem with uniform complex scaling, can reliably perform bound-to-resonance extrapolations for genuine three-body resonances having no bound subsystems. We first establish that three-body bound-to-resonance extrapolations are possible by benchmarking different few-body approaches, and we provide arguments to explain how the extrapolation works in the many-body case. We furthermore pave the way towards scalable resonance extrapolations in many-body systems by showing that the CA-EC method also works in the Berggren basis, studying a realistic application using the Gamow shell model.

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arXiv2023

Eigenvector continuation for emulating and extrapolating two-body resonances

The study of open quantum systems (OQSs), i.e., systems interacting with an environment, impacts our understanding of exotic nuclei in low-energy nuclear physics, hadrons, cold-atom systems, or even noisy intermediate-scale quantum computers. Such systems often exhibit resonance states characterized by energy positions and dispersions (or decay widths), the properties of which can be difficult to predict theoretically due to their coupling to the continuum of scattering states. Dealing with this phenomenon poses challenges both conceptually and numerically. For that reason, we investigate how the reduced basis method known as eigenvector continuation (EC), which has emerged as a powerful tool to emulate bound and scattering states in closed quantum systems, can be used to study resonance properties. In particular, we present a generalization of EC that we call conjugate-augmented eigenvector continuation, which is based on the complex-scaling method and designed to predict Gamow-Siegert states, and thus resonant properties of OQSs, using only bound-state wave functions as input.

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