Investigating the Impact of Higher-Order Phase Transitions in Binary Neutron-Star Mergers

TL;DR

This study explores how higher-order phase transitions in dense matter affect neutron star mergers and their gravitational wave signals, providing insights into the microscopic physics of quark deconfinement.

Contribution

It introduces a novel approach to model phase transitions as higher-order, smooth transitions instead of first-order, and investigates their impact on neutron star merger dynamics.

Findings

Higher-order phase transitions alter merger evolution.

Differences observed in gravitational wave signatures.

Potential to better understand dense matter physics.

Abstract

In this paper we investigate quark deconfinement in neutrons stars and their mergers, focusing on the effects of higher orders for the phase transition between hadronic and quark matter. The different descriptions we use to describe matter microscopically contain varying particle degrees of freedom, including nucleons, hyperons, Delta baryons, and light and strange quarks. We use tabulated equations of state from the CompOSE database in which the quark deconfinement phase transition is described as being first-order, and then smooth it out by introducing a percolation, replacing the single first-order phase transition with two transitions of second or third order. We then perform binary neutron-star merger simulations using these new equations of st ate, focusing on groups of binaries with the same single-star mass, radius, and tidal deformability, but different equations of state. We go on to discuss differences in their evolution, and the ramifications for interpreting future gravitational wave observations and the potential to learn about dense matter.