Combined Thesis Feed
https://feeds.library.caltech.edu/people/Marković-D/combined_thesis.rss
A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenWed, 07 Feb 2024 04:19:21 +0000Black holes in the early universe, in compact binaries, and as energy sources inside solar-type stars
https://resolver.caltech.edu/CaltechTHESIS:05092013-084229368
Authors: {'items': [{'id': 'Marković-D', 'name': {'family': 'Marković', 'given': 'Dragoljub'}, 'show_email': 'NO'}]}
Year: 1994
DOI: 10.7907/ms5q-kt36
<p>This thesis consists of three separate studies of roles that black holes might
play in our universe. </p>
<p>In the first part we formulate a statistical method for inferring the cosmological
parameters of our universe from LIGO/VIRGO measurements of the gravitational
waves produced by coalescing black-hole/neutron-star binaries. This method is
based on the cosmological distance-redshift relation, with "luminosity distances"
determined directly, and redshifts indirectly, from the gravitational waveforms.
Using the current estimates of binary coalescence rates and projected "advanced"
LIGO noise spectra, we conclude that by our method the Hubble constant should
be measurable to within an error of a few percent. The errors for the mean density
of the universe and the cosmological constant will depend strongly on the size of
the universe, varying from about 10% for a "small" universe up to and beyond
100% for a "large" universe. We further study the effects of random gravitational
lensing and find that it may strongly impair the determination of the cosmological
constant. </p>
<p>In the second part of this thesis we disprove a conjecture that black holes cannot
form in an early, inflationary era of our universe, because of a quantum-field-theory induced
instability of the black-hole horizon. This instability was supposed to arise
from the difference in temperatures of any black-hole horizon and the inflationary
cosmological horizon; it was thought that this temperature difference would make
every quantum state that is regular at the cosmological horizon be singular at
the black-hole horizon. We disprove this conjecture by explicitly constructing a
quantum vacuum state that is everywhere regular for a massless scalar field. We
further show that this quantum state has all the nice thermal properties that one
has come to expect of "good" vacuum states, both at the black-hole horizon and
at the cosmological horizon. </p>
<p>In the third part of the thesis we study the evolution and implications of a hypothetical
primordial black hole that might have found its way into the center of the
Sun or any other solar-type star. As a foundation for our analysis, we generalize
the mixing-length theory of convection to an optically thick, spherically symmetric
accretion flow (and find in passing that the radial stretching of the inflowing fluid
elements leads to a modification of the standard Schwarzschild criterion for convection).
When the accretion is that of solar matter onto the primordial hole, the
rotation of the Sun causes centrifugal hangup of the inflow near the hole, resulting
in an "accretion torus" which produces an enhanced outflow of heat. We find, however, that the turbulent viscosity, which accompanies the convective transport
of this heat, extracts angular momentum from the inflowing gas, thereby buffering
the torus into a lower luminosity than one might have expected. As a result, the
solar surface will not be influenced noticeably by the torus's luminosity until at
most three days before the Sun is finally devoured by the black hole. As a simple
consequence, accretion onto a black hole inside the Sun cannot be an answer to
the solar neutrino puzzle. </p>
https://thesis.library.caltech.edu/id/eprint/7688