A mixing interpolation method to mimic pasta phases in compact star matter

TL;DR

This paper introduces a new interpolation method for modeling mixed phases in compact star matter, capturing pasta structures and phase transitions, and tests its impact on neutron star properties.

Contribution

A novel interpolation approach for mixed phases in compact stars that models pasta structures and phase transitions more accurately.

Findings

The method effectively models pasta phases in neutron star matter.

It demonstrates robustness of mass twin phenomena with pasta phase inclusion.

The approach aligns with known pasta phase behaviors in neutron star crusts.

Abstract

We present a new method to interpolate between two matter phases that allows for a description of mixed phases and can be used, e.g., for mimicking transitions between pasta structures occuring in the crust as well as in the inner core of compact stars. This interpolation method is based on assuming switch functions that are used to define a mixture of subphases while fulfilling constraints of thermodynamic stability. The width of the transition depends on a free parameter, the pressure increment relative to the critical pressure of a Maxwell construction. As an example we present a trigonometric function ansatz for the switch function together with a pressure increment during the transition. We note that the resulting mixed phase equation of state bears similarities with the appearance of substitutional compounds in neutron star crusts and with the sequence of transitions between different pasta phases in the hadron-to-quark matter transition. We apply this method to the case of a hadron-to-quark matter transition and test the robustness of the compact star mass twin phenomenon against the appearance of pasta phases modeled in this way.