# ROSE: A reduced-order scattering emulator for optical models

**Authors:** Daniel Odell, Pablo Giuliani, Kyle Beyer, Manuel Catacora-Rios, Moses Y. -H. Chan, Edgard Bonilla, Richard J. Furnstahl, Kyle Godbey, Filomena M. Nunes  
**arXiv:** [2312.12426](https://arxiv.org/abs/2312.12426)  
**Date:** 2023-12-19  
**Summary page:** https://www.summarizepaper.com/en/paper/2312.12426v1/

## Key points

- Understanding basic information about nuclei in nuclear reactions requires validated reaction models
- Ab initio methods are effective for light ions but fall short for heavier systems
- Many-body methods are often reduced to few-body problems using optical potentials, introducing uncertainties in reaction analyses
- Recent studies emphasize the need for a global optical potential valid across the nuclear chart with quantified uncertainties
- Bayesian frameworks help quantify uncertainties and design experiments effectively
- Emulators provide fast and accurate approximations in Bayesian studies, such as the Reduced Order Scattering Emulator (ROSE)
- ROSE within the BAND Framework software suite is valuable for uncertainty quantification in nuclear reactions by handling non-linear parameters like those found in optical potentials
- ROSE offers controlled trade-offs between speed and accuracy compared to high-fidelity solvers
- Planned extensions aim to enhance ROSE's capabilities further for complex scattering problems involving different energies or interactions with optical potentials

## Summary

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In the field of nuclear reactions, understanding basic information about nuclei such as energy levels and distribution of matter requires validated reaction models. Current ab initio methods are effective for light ions, but fall short when applied to heavier systems. To address this limitation, many-body methods are often reduced to few-body problems with the help of optical potentials. However, these introduce significant uncertainties in reaction analyses. Recent studies have emphasized the need for a global optical potential valid across the nuclear chart with quantified uncertainties. Bayesian frameworks have been employed to quantify these uncertainties and design experiments effectively. Traditional computational methods become time-consuming for numerous evaluations in Bayesian studies, making emulators a valuable alternative by providing fast and accurate approximations. The Reduced Order Scattering Emulator (ROSE) has been introduced to handle non-linear parameters like those found in optical potentials within the BAND Framework software suite for calibration, model mixing, and experimental design. It offers controlled trade-offs between speed and accuracy compared to high-fidelity solvers, making it valuable for uncertainty quantification in nuclear reactions. Planned extensions aim to enhance its capabilities further for complex scattering problems involving different energies or interactions with optical potentials. Overall, ROSE represents a significant advancement in emulators for nuclear reaction studies and uncertainty quantification in phenomenological optical models.