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Articles 1 - 6 of 6
Full-Text Articles in Cosmology, Relativity, and Gravity
The Black-To-White Hole Transition, Farshid Soltani
The Black-To-White Hole Transition, Farshid Soltani
Electronic Thesis and Dissertation Repository
Classically, an isolated black hole is a stable gravitational object. If however semiclassical effects are taken into account, an isolated black hole can be shown to slowly radiate its mass away in a process called evaporation. At the end of the evaporation process, when the size of the horizon becomes Planckian, the quantum nature of the gravitational field can no longer be neglected and the dynamics of the horizon is governed by quantum gravity. The main objective of this thesis is the systematic investigation of a tentative scenario for the “end of the life” of a black hole: the black-to-white …
Formation Of Supermassive Black Holes In The Early Universe, Arpan Das
Formation Of Supermassive Black Holes In The Early Universe, Arpan Das
Electronic Thesis and Dissertation Repository
The aim of the work presented in this thesis is to understand the formation and growth of the seeds of the supermassive black holes in early universe. Supermassive black holes (SMBH) with masses larger than 108MSun have been observed when the Universe was only 800 Myr old. The formation and accretion history of the seeds of these supermassive black holes are a matter of debate. We consider the scenario of massive seed black hole formation which allows gas to directly collapse into a black hole (DCBH) of similar mass. Considering this scenario, we show that the mass …
Probabilistic Reasoning In Cosmology, Yann Benétreau-Dupin
Probabilistic Reasoning In Cosmology, Yann Benétreau-Dupin
Electronic Thesis and Dissertation Repository
Cosmology raises novel philosophical questions regarding the use of probabilities in inference. This work aims at identifying and assessing lines of arguments and problematic principles in probabilistic reasoning in cosmology.
The first, second, and third papers deal with the intersection of two distinct problems: accounting for selection effects, and representing ignorance or indifference in probabilistic inferences. These two problems meet in the cosmology literature when anthropic considerations are used to predict cosmological parameters by conditionalizing the distribution of, e.g., the cosmological constant on the number of observers it allows for. However, uniform probability distributions usually appealed to in such arguments …
Rationality Of The Spectral Action For Robertson-Walker Metrics And The Geometry Of The Determinant Line Bundle For The Noncommutative Two Torus, Asghar Ghorbanpour
Rationality Of The Spectral Action For Robertson-Walker Metrics And The Geometry Of The Determinant Line Bundle For The Noncommutative Two Torus, Asghar Ghorbanpour
Electronic Thesis and Dissertation Repository
In noncommutative geometry, the geometry of a space is given via a spectral triple $(\mathcal{A,H},D)$. Geometric information, in this approach, is encoded in the spectrum of $D$ and to extract them, one should study spectral functions such as the heat trace $\Tr (e^{-tD^2})$, the spectral zeta function $\Tr(|D|^{-s})$ and the spectral action functional, $\Tr f(D/\Lambda)$.
The main focus of this thesis is on the methods and tools that can be used to extract the spectral information. Applying the pseudodifferential calculus and the heat trace techniques, in addition to computing the newer terms, we prove the rationality of the spectral action …
Observational Signatures From Self-Gravitating Protostellar Disks, Alexander L. Desouza
Observational Signatures From Self-Gravitating Protostellar Disks, Alexander L. Desouza
Electronic Thesis and Dissertation Repository
Protostellar disks are the ubiquitous corollary outcome of the angular momentum conserving, gravitational collapse of molecular cloud cores into stars. Disks are an essential component of the star formation process, mediating the accretion of material onto the protostar, and for redistributing excess angular momentum during the collapse. We present a model to explain the observed correlation between mass accretion rates and stellar mass that has been inferred from observations of intermediate to upper mass T Tauri stars. We explain this correlation within the framework of gravitationally driven torques parameterized in terms of Toomre’s Q criterion. Our models reproduce both the …
An Analytical And Numerical Treatment Of Inclined Elliptical Orbits About A Kerr Black Hole, Peter G. Komorowski
An Analytical And Numerical Treatment Of Inclined Elliptical Orbits About A Kerr Black Hole, Peter G. Komorowski
Electronic Thesis and Dissertation Repository
Since its publication in 1915, Einstein's theory of general relativity has yielded significant results; they include: analytical solutions to the Einstein field equations; improved analysis of orbital dynamics; and the prediction of gravitational wave (GW) radiation. Gravitation is the weakest of the fundamental interactions; and theoretical models of GW generation and propagation show that its detection poses a significant technical challenge. Unlike the study of electromagnetic radiation, experiments within the laboratory are virtually impossible; so astronomical sources of GW, such as binary black hole systems, offer an alternative. But GW detection remains difficult. The matched filtering techniques used to discriminate …