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

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.