The Neutrino Sector in Hadron-Quark Combustion: Physical and Astrophysical Implications
Date
2019-01-25
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Abstract
The high densities inside the cores of neutron stars may lead to the melting of hadrons (e.g. protons and neutrons) into their constituent quarks - in other words, a phase transition from hadronic to quark matter. Under the hypothesis of absolutely stable three-flavoured quark matter (3QM), i.e. bulk quark matter made of up, down, and strange quarks, this transition can lead to a powerful release of 10^{53} erg (the same energetics of core-collapse supernova) in kinetic energy, photons and neutrinos. Such a transition would be spectacular from an observational perspective, and would also shed some light on issues related to astrophysics and particle physics. Since a much of the energy released by the hadron-quark phase transition is in the form of neutrinos, this thesis will focus on the neutrino physics of that conversion process. The thesis will be divided into two parts. In Part 1: Microphysics I explore how the neutrinos couple to the reaction zone, which is the ∼ 1 cm wide interface were the hadrons are converted into quarks. High energy neutrinos (∼ 100 MeV) are coupled to this zone. The scales for the reaction zone are a length-scale of l ∼ 1 cm which corresponds to the width of the reaction zone, and a timescale of τ_W ∼ 10^{−8}s which corresponds to the scale of chemical equilibration of the quark matter. In Part II: Macrophysics, I focus on the larger scales of the whole compact object that is left behind after the neutron star converts into a hot, proto-quark star (PQS). The relevant scales of this problem are the radius of the PQS (R ∼ 10 km) and the time it takes for neutrinos to diffuse from the centre of the PQS to the edge (τ_C ∼ 10 s). For Part I: Microphysics, I solved the Partial Differential Equations (PDEs) that govern the combustion of hadronic to 3QM. This thesis is the first work to include neutrino transport and a realistic hadronic EOS in a time-dependent, hydrodynamic simulation. These simulations show that neutrino physics couple non-linearly to the system, and can lead to a deleptonization instability an instability that was previously hinted at through semi-analytic, parameterized arguments Niebergal et al. (2010), but which I explore for the first time in a time-dependent, numerical simulation. One important result of this work is the derivation of a proof of the soundness of this instability through a linear stability analysis. Furthermore, I discovered that the inclusion of a hadronic EOS can generate non-linear thermodynamic effects where the coupling of neutrino transport and the free energy of the hadronic EOS can lead to quenching. This quenching appears since the hadronic fuel can absorb neutrinos emitted by the hot 3QM, which can lead to the erection of a free energy barrier that makes combustion thermodynamically unfavourable. These results hint that a multidimensional code is necessary, since instability would lead to a wrinkling of the interface, and therefore only through a multidimensional study can we unearth the final fate of the compact star. For Part II: Macrophysics, I ran a stellar evolution code, where the evolution of a hot proto-quark star is studied. The novelty of my approach is the interpolation of the temperatures calculated from Part I: Microphysics into the large-scale, R ∼ 10 km stellar evolution code. My approach leads to much higher peak neutrino luminosities (> 10^{55} erg/s) and a higher energy neutrino spectrum than previous stellar evolution studies on PQS Pagliara et al. (2013). I also calculated for the first time, the neutrino counts that observatories such as Super-Kamiokande-III and Halo-2 should expect. Finally, I find that due to the high peak neutrino luminosities, neutrino pair annihilation can deposit as much as ∼ 10^{52} erg in kinetic energy in the matter overlaying the neutrinosphere.
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Keywords
quarks, combustion, neutron star, quark star, nonlinear
Citation
Ouyed Hernandez, A. H. (2019). The Neutrino Sector in Hadron-Quark Combustion: Physical and Astrophysical Implications (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.