The equation of state for dense nucleonic matter from a metamodeling. I. Foundational aspects

TL;DR

This paper introduces a flexible metamodeling approach for the nuclear equation of state based on empirical parameters, enabling uncertainty quantification and exploration of density dependences relevant for neutron stars and supernovae.

Contribution

It develops a novel metamodeling framework for the nucleonic EOS using a Taylor expansion, allowing comprehensive uncertainty analysis and removal of spurious correlations.

Findings

The isovector parameters $L_{sym}$ and $K_{sym}$ are most influential.

Laboratory constraints at high densities are crucial for reducing uncertainties.

The metamodeling accurately reproduces original model predictions.

Abstract

A metamodeling for the nucleonic equation of state (EOS), inspired from a Taylor expansion around the saturation density of symmetric nuclear matter, is proposed and parameterized in terms of the empirical parameters. The present knowledge of nuclear empirical parameters is first reviewed in order to estimate their average values and associated uncertainties, and thus defining the parameter space of the metamodeling. They are divided into isoscalar and isovector type, and ordered according to their power in the density expansion. The goodness of the metamodeling is analyzed against the predictions of the original models. In addition, since no correlation among the empirical parameters is assumed a priori, all arbitrary density dependences can be explored, which might not be accessible in existing functionals. Spurious correlations due to the assumed functional form are also removed. This meta-EOS allows direct relations between the uncertainties on the empirical parameters and the density dependence of the nuclear equation of state and its derivatives, and the mapping between the two can be done with standard Bayesian techniques. A sensitivity analysis shows that the more influential empirical parameters are the isovector parameters $L_{sym}$ and $K_{sym}$, and that laboratory constraints at super-saturation densities are essential to reduce the present uncertainties. The present metamodeling for the EOS for nuclear matter is proposed for further applications in neutron stars and supernova matter.