Date of Award

Spring 2025

Project Type

Dissertation

Program or Major

Physics

Degree Name

Doctor of Philosophy

First Advisor

Chanda Prescod-Weinstein

Second Advisor

Francois Foucart

Third Advisor

Elena Long

Abstract

The combination of derived neutron star mass-radius measurements from NASA's Neutron Star Interior Composition ExploreR (NICER) mission, constraints from chiral effective field theory (chiEFT), and mass-tidal deformability constraints from gravitational waves has led to significant improvements in the understanding of the cold dense matter equation of state (EoS) of neutron stars. Interestingly, asymmetric dark matter (ADM) and dark energy may also be present within neutron star interiors, potentially impacting their global properties. Taking these effects into account, neutron star measurements can not only offer new insights into the dense matter EoS, but also serve as a hunting ground for dark matter and dark energy.

In this dissertation, we first develop a Bayesian data analysis pipeline for inferring the ADM admixed neutron star EoS and demonstrate the possibility of constraining bosonic ADM cores using synthetic mass-radius measurements from current and future X-ray telescopes. Building on this Bayesian framework, we extend our prior work by incorporating both real and synthetic neutron star mass-radius data and investigate the constraints on the combined baryonic matter and fermionic ADM EoS. Next, we consider the possibility of neutron stars with a dark energy core surrounded by a baryonic matter shell, where the dark energy is taken to be the modified Chaplygin dark fluid (MCDF). In particular, we explore the effects of MCDF cores, as well as ADM cores with large mass ratios relative to the total mass of the star, on the inferred neutron star EoS and observables. Lastly, we turn our attention to constraining the baryonic EoS using two different high-density EoS parameterizations--a piecewise-polytropic (PP) model and a model based on the speed of sound in the neutron star interior (CS). Using these models, we assess the impact of several new results on the inferred baryonic EoS, including updates to the mass-radius measurements of PSR J0740+6620 and PSR J0030+0451, new chiEFT results for neutron star matter up to 1.5 times nuclear saturation density, and, most recently, the mass-radius measurement of PSR J0437-4715.

Download

Share

COinS