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

TL;DR

This paper introduces a scalable method using complex-augmented eigenvector continuation to reliably extrapolate bound states to resonances in few- and many-body quantum systems, with applications to nuclear and hadronic physics.

Contribution

It demonstrates that the CA-EC method can perform bound-to-resonance extrapolations for three-body and many-body systems, extending its applicability to realistic nuclear models.

Findings

CA-EC reliably performs bound-to-resonance extrapolations.

The method works in the Berggren basis for many-body systems.

Application demonstrated with the Gamow shell model.

Abstract

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.