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Neutrino Radiation Transport and Other Topics in High Energy Density Astrophysics

Citation

Richers, Sherwood Andrew (2018) Neutrino Radiation Transport and Other Topics in High Energy Density Astrophysics. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9PC30JH. http://resolver.caltech.edu/CaltechTHESIS:07212017-001528247

Abstract

Neutron star mergers and the collapse of massive stars result in some of the universe’s most violet explosions. However, the detailed mechanisms behind all of these astrophysical explosions remain elusive. Their strongly nonlinear and complicated nature makes them difficult and expensive to simulate, and the properties of matter in these extreme conditions are poorly constrained. I use a variety of computational tools to understand the detailed mechanisms behind both types of events.

I describe my relativistic time-independent multidimensional Monte Carlo neutrino radiation transport code Sedonu that provides an accurate account of the neutrino radiation fields and the interaction with neutrinos and background fluid. Though Sedonu calculations are time-independent, I demonstrate their utility in dynamical general relativistic variable Eddington tensor radiation hydrodynamics simulations.

I apply Sedonu to simulations of accretion disks following neutron star mergers to demonstrate that more realistic disk cooling and neutrino-driven mass ejection rates are larger than is predicted using approximate transport methods. I also reinforce that neutrino pair annihilation from these disk configurations is unlikely to be able to energize a gamma-ray burst jet.

I subject Sedonu to the first thorough comparison of Boltzmann neutrino radiation transport methods in multiple spatial dimensions in the context of core-collapse supernovae. The comparisons with the other highly accurate discrete ordinates-based transport scheme show remarkably similar results, verifying the accuracy of both methods and underscoring the importance of numerical fidelity.

I perform the first broad parameter study on how different descriptions of dense nuclear matter and star rotation rates influence the dynamics of, and hence gravitational waves from, the bounce and early post-bounce phase of rapidly rotating core collapse supernovae. Using the results of 1824 two-dimensional general relativistic core-collapse simulations, I demonstrate that the equation of state is unlikely to be constrained by LIGO observations. I show that the effect of the equation of state on the gravitational wave frequency can be described by a single universal relation.

Finally, I use results of three-dimensional general relativistic magnetohydrodynamics simulations of rapidly rotating core collapse to demonstrate that the polar magnetic structures that form are destroyed by a magnetohydrodynamic kink instability.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:neutrinos; supernovae; radiation transport; gravitational waves
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Astrophysics
Research Advisor(s):
  • Ott, Christian D.
Group:TAPIR
Thesis Committee:
  • Ott, Christian D. (chair)
  • Hopkins, Philip F.
  • Filippone, Bradley W.
  • Kulkarni, Shrinivas R.
  • Kasen, Daniel
Defense Date:29 June 2017
Funders:
Funding AgencyGrant Number
Department of Energy Computational Science Graduate Fellowship (DOE-CSGF)UNSPECIFIED
Blue Waters Graduate FellowshipUNSPECIFIED
Record Number:CaltechTHESIS:07212017-001528247
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:07212017-001528247
DOI:10.7907/Z9PC30JH
Related URLs:
URLURL TypeDescription
https://doi.org/10.1088/0004-637X/813/1/38DOIArticle adapted for ch. 4
https://doi.org/10.1088/2041- 8205/785/2/L29DOIArticle adapted for ch. 6
https://doi.org/10.1103/PhysRevD.95.063019DOIArticle adapted for ch. 7
ORCID:
AuthorORCID
Richers, Sherwood Andrew0000-0001-5031-6829
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10347
Collection:CaltechTHESIS
Deposited By: Sherwood Richers
Deposited On:28 Jul 2017 16:27
Last Modified:18 Aug 2017 20:57

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