Toward emulating nuclear reactions using eigenvector continuation

TL;DR

This paper develops an efficient emulator for two-body scattering observables using eigenvector continuation and the Kohn variational principle, enabling improved optical model predictions and uncertainty quantification.

Contribution

It introduces a novel emulator combining eigenvector continuation with the Kohn variational principle to accurately and efficiently compute scattering observables, reducing numerical noise and handling singularities.

Findings

Successfully emulates differential cross sections for $^{40}$Ca$(n,n)$ scattering.

Quantifies model uncertainties using Bayesian methods.

Reduces numerical noise compared to previous methods.

Abstract

We construct an efficient emulator for two-body scattering observables using the general (complex) Kohn variational principle and trial wave functions derived from eigenvector continuation. The emulator simultaneously evaluates an array of Kohn variational principles associated with different boundary conditions, which allows for the detection and removal of spurious singularities known as Kohn anomalies. When applied to the $K$-matrix only, our emulator resembles the one constructed by Furnstahl et al. [Phys. Lett. B 809, 135719] although with reduced numerical noise. After a few applications to real potentials, we emulate differential cross sections for $^{40}$Ca$(n,n)$ scattering based on a realistic optical potential and quantify the model uncertainties using Bayesian methods. These calculations serve as a proof of principle for future studies aimed at improving optical models.