Parametric Representations of Neutron-Star Equations of State With Phase Transitions

TL;DR

This paper evaluates parametric models for neutron-star equations of state with phase transitions, finding that piecewise-analytic methods converge well and spectral methods are more accurate at lower orders despite non-convergence.

Contribution

It introduces and compares low-dimensional parametric representations for neutron-star equations of state with phase transitions, highlighting their convergence and accuracy properties.

Findings

Piecewise-analytic representations are convergent for non-smooth equations.

Spectral representations are more accurate at low parameter counts.

Lower-order spectral models outperform piecewise-analytic models with the same parameters.

Abstract

This paper explores the use of low-dimensional parametric representations of neutron-star equations of state that include discontinuities caused by phase transitions. The accuracies of optimal piecewise-analytic and spectral representations are evaluated for equations of state having first- or second-order phase transitions with a wide range of discontinuity sizes. These results suggest that the piecewise-analytic representations of these non-smooth equations of state are convergent, while the spectral representations are not. Nevertheless, the lower-order (2 <= N_parms <= 7) spectral representations are found to be more accurate than the piecewise-analytic representations with the same number of parameters.