Studying Compact Star Equation Of States With General Relativistic Initial Data Approach PDF Download

Compact stars (CSs) are the remnants of "dead" stars that were too small to form black holes; the category includes both white dwarfs (WDs) and neutron stars (NSs). To produce a full description of any magnetized compact star requires solving Einstein's equations in unison with Maxwell's equations. However, when putting these two sets of equations together, there is an additional degree of freedom that requires the inclusion of the equation of state (EOS) of the stellar matter in question. The most notable difference between CSs and other stars is that CSs consist of degenerate fermion matter. Fermionic matter exists in a degenerate state when the temperature is low compared to the Fermi energy. Such states arise due to the Pauli exclusion principle, which states that no two identical fermions (particles with half integer spin) in the same quantum system may inhabit the same quantum state. In the case of WDs, this degeneracy is caused solely by electrons; whereas, in NSs, the degeneracy is in several species of particles including neutrons and protons, but also more "exotic" baryons, such as Lambdas, Sigmas, and Cascades. In the grand canonical ensemble, the stellar EOS is typically expressed as the relation between the total energy density of a gas of particles and their pressure. It is calculated using thermodynamics with, in the NS case, an additional contribution from the strong nuclear force, which must be modeled. Due to computational difficulty, the EOS is often calculated in a simplified way, assuming that one aspect or another is not significant. As such, EOSs exist with temperature effects or with magnetic field effects, but not with both. For example, higher temperatures (without additional degrees of freedom) lead to higher pressures at the same energy density; the EOS is "stiffer." Magnetic fields lead to a pressure anisotropy and Landau quantization, which gives rise to De Haas-Van Alphen oscillations in the EOS. This thesis breaks new ground by simultaneously including both temperature and magnetic field effects into the EOS of compact stars. The thermodynamic portion of the EOS is calculated by treating the particles as a relativistic free Fermi gas, in which, particles are treated as non-interacting and must obey Fermi-Dirac statistics. This approach also allows for the calculation of other thermodynamic quantities, such as number density, entropy density, and magnetization. Contributions from the strong force are calculated using the chiral mean field (CMF) model for neutron stars. The CMF model is a relativistic effective model based on a non-linear realization of the linear sigma model of Quantum Chromodynamics (QCD). It features hadron deconfinement into quarks and self-consistent chiral symmetry restoration. Each fundamental force is thought to have a force carrying boson (particles with integer spin, not subject to Pauli exclusion). The photon is the carrier for the electromagnetic force and the carrier for the strong nuclear force is the gluon. In the CMF model, gluons are approximated as "mesons," which are exchanged between hadrons and quarks. As a result, these mesons acquire some properties from both gluons and quarks. Note that, due to the high density and low temperature of NS matter, standard QCD approaches fail to provide an adequate description. Lattice QCD exhibits the sign problem at non-zero baryon density, due to integrating highly oscillating functions. Perturbative QCD breaks down in the presence of strong particle interactions. These are both conditions found in NSs. Finally, this thesis investigates the EOS for isospin-symmetric matter (equal numbers of protons and neutrons or up and down quarks), to reproduce conditions found in heavy ion collisions (HICs). While HICs do not create matter with net density comparable to that of CSs, the energy density is comparable to that of CSs due to their relativistic speeds. This makes HICs the closest we can get to creating CS matter on Earth.