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Dissertations / Theses on the topic 'Cosmological models'

Author: Grafiati

Published: 4 June 2021

Last updated: 25 July 2025

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1

Müller, Christian Mathias. "Cosmological models and observation." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975799193.

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2

Campbell, Robert Alan. "Inhomogeneous conformal cosmological models /." Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09phc1888.pdf.

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3

PINTUS, NICOLA. "On Inflationary cosmological models." Doctoral thesis, Università degli Studi di Cagliari, 2016. http://hdl.handle.net/11584/266648.

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The most common mechanisms leading to in ation are based on models of gravity minimally coupled to a scalar field rolling on a suitable potential V. We discuss such a model defined by the action I = ∫√-g p [R -2 (ϕ)2 )] d4x, in order to find exact general isotropic and homogeneous cosmological solutions displaying an in ationary behavior at early times and a power-law expansion at late times. We also study the effect of the inclusion of matter (in the form of a perfect uid): in this case, we do not find exact solutions because of the non-integrability of the field equations, but we

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4

Barnaby, Neil. "Cosmological instabilities." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103365.

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Though historically the word "tachyon" has been used to describe hypothetical particles which propagate faster than the speed of light, in a more modern context the term has been recycled to refer to certain unstable states in field theory. This thesis explores the role of tachyonic instabilities in cosmology considering tachyons which arise in string theory and also more conventional, field theoretic instabilities. Our study of such instabilities is, in part, motivated by attempts to embed inflation into string theory. We will argue that the study of string theory models of inflation is well-

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5

Ghodsi, Hoda. "Constraining non-standard cosmological models." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2998/.

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Current observational evidence does not yet exclude the possibility that dark energy could be in the form of phantom energy. A universe consisting of a phantom constituent will be driven toward a drastic end known as the `Big Rip' singularity where all the matter in the universe will be destroyed. Motivated by this possibility, other evolutionary scenarios have been explored by e.g. Barrow, including the phenomena which he called Sudden Future Singularities (SFS). In a model consisting of such events it is possible to have a blow up of the pressure occurring at sometime in the future evolution

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6

Graham, Christopher Michael. "Testing models of cosmological inflation." Thesis, University of Newcastle Upon Tyne, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512023.

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7

Leeper, Emily. "Dynamics of cosmological braneworld models." Thesis, University of Portsmouth, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425773.

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8

Rhodes, Christophe Sebastian. "Cosmological observations in braneworld models." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615727.

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9

Jörgenfelt, Erik. "Invariant Construction of Cosmological Models." Thesis, Umeå universitet, Institutionen för fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-125403.

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Solutions to the Einstein field equations can be constructed from invariant objects. If a solution is found it is locally equivalent to all solutions constructed from the same set. Here the method is applied to spatially-homogeneous solutions with pre-determined algebras, under the assumption that the invariant frame field of standard vectors is orthogonal on the orbits. Solutions with orthogonal fluid flow of Bianchi type III are investigated and two classes of orthogonal dust (zero pressure) solutions are found, as well as one vacuum energy solution. Tilted dust solutions with non-vanishing

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10

Duran, Sancho Ivan. "Constraining Cosmological Models of Dark Energy." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/125917.

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Avui en dia, l'Univers sembla estar experimentant una fase d'expansió accelerada, com ho demostren les dades de supernoves i posteriorment corroborada per una sèrie de mesuraments cosmològiques -molt recentment pel satèl·lit Planck. Mentre que aquesta expansió pot ser descrit en la teoria de la gravetat d'Einstein mitjançant la invocació de l'existència d'una positiva, però extremadament petita constant cosmològica, Λ, connectat al buit quàntic, s'han proposat moltes alternatives. A grans trets, el contingut d'energia de l'univers actual es pot dividir en 5% de la matèria bariònica i el 95% d'

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11

Clancy, Dominic. "Homogeneous and inhomogeneous superstring cosmological models." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249229.

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12

Pearson, Russell Charles. "The statistical analysis of cosmological models." Thesis, Queen Mary, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264659.

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13

Williams, Jolin Shan. "Dynamics of Discrete Irregular Cosmological Models." Thesis, Stockholms universitet, Fysikum, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-110841.

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This thesis investigates the dynamics of a set of 8-600 Schwarzschild masses, randomly distributed inside cells which tessellate a 3-sphere. Furthermore the contents of each cell are mirror images of its neighbor. This symmetry give rise to a locally rotationally symmetric (LRS) curve, along which the Einstein field equations governing dynamics can be exactly integrated. The result is an irregular model consisting of discrete matter content, but where the dynamics is easy to calculate. We see that these local inhomogeneities will cause behavior deviating from the spherical dust-filled FLRW mod

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14

Cotsakis, Spiros. "Cosmological models in higher-order gravity." Thesis, University of Sussex, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303168.

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15

Friedrichsen, James Edward. "Quantization of Bianchi type cosmological models /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004268.

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16

Mimoso, Jose Pedro. "Cosmological models of the early universe." Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358557.

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17

Bernardo, Heliudson de Oliveira. "Cosmological models from string theory setups /." São Paulo, 2019. http://hdl.handle.net/11449/183612.

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Orientador: Horatiu Nastase<br>Resumo: Nesta tese, discutimos três modelos cosmológicos que são baseados direta ou indiretamente em ideias advindas de teoria das cordas. Depois de uma revisão geral de cosmologia em teoria das cordas, um resumo de cosmologia e teoria das cordas é apresentado, com ênfase nos conceitos fundamentais e teóricos. Então descrevemos como o acoplamento camaleônico pode potencialmente afetar as predições de inflação cósmica com campo único, com tratamento cuidadoso dos modos de perturbação cosmológica adiabáticos e de entropia. Além disso uma nova abordagem para a duali

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18

Saro, Alexandro. "Galactic population in cosmological hierarchical models." Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3066.

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2007/2008<br>Il lavoro di ricerca è stato orientato allo studio delle proprietà delle strutture su grande scala dell'Universo. In particolar modo si sono studiate le proprietà ottiche e fisiche di popolazioni sintetiche di galassie in ammassi di galassie in ambito cosmologico all'interno dello scenario gerarchico. Abbiamo affrontato il problema della formazione galattica seguendo due approcci complementari. Una linea di ricerca svolta è stata indirizzata allo studio della popolazione galattica in ammassi di galassie, utilizzando simulazioni idrodinamiche cosmologiche. A tale scopo si sono a

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19

Sobacchi, Emanuele. "Sub-grid models of cosmological reionization." Doctoral thesis, Scuola Normale Superiore, 2016. http://hdl.handle.net/11384/86198.

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20

Paul, Dilip. "Cosmological models of the Early universe." Thesis, University of North Bengal, 2009. http://hdl.handle.net/123456789/1407.

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21

McNally, Stephen John. "Testing the models of cosmological structure formation." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/28602.

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The first half of chapter 1 exposes the most significant grey areas in the Standard Hot Big Bang model: (a) determining the form and density of the energy content of the Universe, and reconciling this to (b) the age of the Universe, and (c) the observed clustering of galaxies. This thesis makes two contributions to this area. Chapter 2 discusses a variant of the Cold Dark Matter model in which a dark matter component decays radiatively at early times. The model has the virtue that it can accommodate the <I>low</I> value of Ω<I>h</I> inhered from observed large-scale galaxy clustering and the <

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22

Allen, Laura. "Cosmological perturbations : constraining models of the universe." Thesis, University of Portsmouth, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439040.

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23

Saich, Paul John. "Cosmological models and the formation of structure." Thesis, University of Sussex, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385670.

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24

Sandin, Patrik. "Cosmological Models and Singularities in General Relativity." Doctoral thesis, Karlstads universitet, Avdelningen för fysik och elektroteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-8206.

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This is a thesis on general relativity. It analyzes dynamical properties of Einstein's field equations in cosmology and in the vicinity of spacetime singularities in a number of different situations. Different techniques are used depending on the particular problem under study; dynamical systems methods are applied to cosmological models with spatial homogeneity; Hamiltonian methods are used in connection with dynamical systems to find global monotone quantities determining the asymptotic states; Fuchsian methods are used to quantify the structure of singularities in spacetimes without symmetr

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25

Hanimeli, Ekim Taylan. "Test Of Cosmological Models With Variable G." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70836.

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26

Ambrogi, Federico. "Bispectrum of cosmological models with massive neutrinos." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7429/.

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Uno dei più importanti campi di ricerca che coinvolge gli astrofisici è la comprensione della Struttura a Grande Scala dell'universo. I principi della Formazione delle Strutture sono ormai ben saldi, e costituiscono la base del cosiddetto "Modello Cosmologico Standard". Fino agli inizi degli anni 2000, la teoria che spiegava con successo le proprietà statistiche dell'universo era la cosiddetta "Teoria Perturbativa Standard". Attraverso simulazioni numeriche e osservazioni di qualità migliore, si è evidenziato il limite di quest'ultima teoria nel descrivere il comportamento dello spettro di po

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27

Sandin, Patrik. "The asymptotic states of perfect fluid cosmological models." Licentiate thesis, Karlstad : Faculty of Technology and Science, Physics, Karlstads universitet, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-4713.

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28

Choi, Wai-fung. "Reheating the universe in brane world cosmological models." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B39376795.

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29

Choi, Wai-fung, and 蔡偉峰. "Reheating the universe in brane world cosmological models." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39376795.

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30

Elghozi, Thomas André Claude. "Astrophysical and cosmological consequences of string-inspired models." Thesis, King's College London (University of London), 2017. https://kclpure.kcl.ac.uk/portal/en/theses/astrophysical-and-cosmological-consequences-of-stringinspired-models(da218836-7682-4995-9410-58738236fde3).html.

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The standard model of cosmology, namely the CDM model, is based on Einstein's theory of General Relativity (GR) with a Cold Dark Matter (CDM) content and a positive cosmological constant , in addition to ordinary matter and radiation components. While it provides a paradigm in very good agreement with many observations, from Big Bang Nucleosynthesis (BBN) to Cosmic Microwave Background (CMB), several questions remain open and various theoretical extensions seem necessary in order to address them. An extensively studied ingredient of the CDM model is the inflationary scenario, which solves some

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31

Muia, Francesco <1987&gt. "Sequestered String Models: Supersymmetry Breaking and Cosmological Applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7274/1/Muia_Francesco_Tesi.pdf.

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In the present thesis I focused on the study of the phenomenology arising from a class of string models called sequestered compactifications, which were born with the aim of getting low-energy SUSY from strings. This is not an easy task if combined with cosmological constraints, since the mechanism of moduli stabilization fixes both the scale of supersymmetric particles and the scale of moduli, which tend to be of the same order. However, if on the one hand supersymmetric particles with TeV mass are desired in order to address the electroweak hierarchy problem, on the other hand the cosmologi

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32

Muia, Francesco <1987&gt. "Sequestered String Models: Supersymmetry Breaking and Cosmological Applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7274/.

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In the present thesis I focused on the study of the phenomenology arising from a class of string models called sequestered compactifications, which were born with the aim of getting low-energy SUSY from strings. This is not an easy task if combined with cosmological constraints, since the mechanism of moduli stabilization fixes both the scale of supersymmetric particles and the scale of moduli, which tend to be of the same order. However, if on the one hand supersymmetric particles with TeV mass are desired in order to address the electroweak hierarchy problem, on the other hand the cosmologi

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33

Larsson, Sebastian E. "Topological defects from cosmological phase transitions." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298309.

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34

Jackson, C. B. "Cosmological tests of unified models for extragalactic radio sources." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604987.

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This thesis considers if the current 'unified scheme' for powerful extragalactic radio sources are valid in the light of cosmological tests embodied in radio source count and identification data. Although the analysis is based on the simplest possible parametric descriptions of radio source evolution and beaming, the overall agreement with the available observational data is quite remarkable. The first part of the thesis describes an identification programme of flat-spectrum radio sources at 2.7 GHz. The complete sample provides two important pieces of information (1) whether a turnover in the

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35

Vázquez-González, José-Alberto. "Constraining alternative cosmological models with current and future observations." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648115.

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36

Wei, Jun-Jie, Xue-Feng Wu, and Fulvio Melia. "TESTING COSMOLOGICAL MODELS WITH TYPE Ic SUPER LUMINOUS SUPERNOVAE." IOP PUBLISHING LTD, 2015. http://hdl.handle.net/10150/615104.

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The use of type Ic Super Luminous Supernovae (SLSN Ic) to examine the cosmological expansion introduces a new standard ruler with which to test theoretical models. The sample suitable for this kind of work now includes 11 SLSN Ic's, which have thus far been used solely in tests involving $\Lambda$CDM. In this paper, we broaden the base of support for this new, important cosmic probe by using these observations to carry out a one-on-one comparison between the $R_{\rm h}=ct$ and $\Lambda$CDM cosmologies. We individually optimize the parameters in each cosmological model by minimizing

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37

Gustafsson, Emil. "Simple cosmological models and their descriptions of the universe." Thesis, Linköpings universitet, Matematik och tillämpad matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-153329.

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Cosmology is the study of the universe as a whole, and attempts to describe the behaviour of the universe mathematically. The simplest relativistic cosmological models are derived from Einstein's field equations with the assumptions of isotropy and homogeneity. In this thesis, a few simple cosmological models will be derived and evaluated with respect to their description of our universe i.e., how well they match observational data from e.g., the cosmic background radiation and redshift from distant supernovae. The models are derived from Einstein's field equations, which is why a large portio

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38

Pavlov, Anatoly. "Constraining competing models of dark energy with cosmological observations." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/20345.

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Doctor of Philosophy<br>Department of Physics<br>Bharat Ratra<br>The last decade of the 20th century was marked by the discovery of the accelerated expansion of the universe. This discovery puzzles physicists and has yet to be fully understood. It contradicts the conventional theory of gravity, i.e. Einstein’s General Relativity (GR). According to GR, a universe filled with dark matter and ordinary matter, i.e. baryons, leptons, and photons, can only expand with deceleration. Two approaches have been developed to study this phenomenon. One attempt is to assume that GR might not be the corre

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39

Benhaiem, David. "Non linear gravitational clustering in scale free cosmological models." Paris 6, 2013. http://www.theses.fr/2013PA066653.

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The formation of structures in the universe is one of the major questions in cosmology, and numerical N body simulations are the primary instrument used to probe the non linear clustering. However, analytical understanding of this regime remains limited. To explore this regime we study a family of Einstein de Sitter models with cold power law initial conditions. In practice, this means that we have two control parameters on which we can study the dependance of simple crucial analytical predictions for these models : self similarity of the clustering, and the correlation exponents when this clu

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40

Ng, Shao-Chin Cindy. "Cosmological models with quintessence : dynamical properties and observational constraints." Title page, table of contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phn5758.pdf.

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Bibliography: leaves 100-106. Studies different models of "quintessence", in particular, a quintessence arising from an ultra-light pseudo Nambu-Goldstone boson. Overviews dynamical properties for these models using phase-space analyses to study attractor and tracker solutions. Studies high-redshift type Ia supernovae constraints on these models. Studies the impact of a simple phenomenological model for supernovae luminosity evolution on the PNGB models and the potentials of a future supernovae data set to discriminate the PNGB models over the other quintessence models. Studies gravitational l

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41

Dimastrogiovanni, Emanuela. "Cosmological correlation functions in scalar and vector inflationary models." Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3427056.

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This thesis is centered on three main subjects within the theory of inflation and cosmological perturbations: loop corrections to the power spectrum of curvature fluctuations generated during inflation; evolution of cosmological fluctuations in anisotropic pre-inflationary cosmologies; statistical anisotropy and non-Gaussianity predictions of models of inflation populated with vector fields. Currently, what makes even more interesting the study of 2-nd and higher order corrections to cosmological correlation functions as well as the computation of higher-than-two order correlators, is the almo

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42

Thakur, Prasenjit. "Observational constraints on equation of state parameters for cosmological models of the Universe." Thesis, University of North Bengal, 2014. http://hdl.handle.net/123456789/1618.

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43

Martineau, Patrick. "Topics in cosmological fluctuations : linear order and beyond." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111877.

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The object of this thesis is to present various applications of the theory of cosmological perturbations. Within are contained a number of manuscripts, each concerned with a separate aspect of the theory. The thesis itself begins with a general overview of cosmological perturbation theory designed to be accessible to the non-specialist. Both the classical and quantum first order theory are considered. Back-reaction, via the formalism of the Effective Energy Momentum Tensor (EEMT) is reviewed. Subsequent chapters are more specialized dealing with various applications of the theory. At first ord

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44

Mania, Data. "Constraints on dark energy models from observational data." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/14178.

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Master of Science<br>Department of Physics<br>Bharat Ratra<br>Recent observations in cosmology suggest that the universe is undergoing accelerating expansion. Mysterious component responsible for acceleration is called "Dark Energy" contributing to 70% of total energy density of the universe. Simplest DE model is [Lambda]CDM, where Einstein’s cosmological constant plays role of the dark energy. Despite the fact that it is consistent with observational data, it leaves some important theoretical questions unanswered. To overcome these difficulties different Dark energy models are proposed.

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45

Barone, Alessandro. "The cosmological moduli problem in multi-field string inflationary models." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18080/.

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The 4D low-energy limit of string compactifications is characterised by the ubiquitous presence of string moduli which are new gravitationally coupled scalar fields which develop mass via supersymmetry breaking effects. During inflation it is generically expected that these fields receive large contributions to their mass of order the Hubble constant. They are therefore shifted from their minimum and after the end of inflation start oscillating around it behaving as non-relativistic matter. Given that matter redshifts slower than radiation, the moduli quickly come to dominate the energy densit

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46

López, Revelles Antonio Jesús. "Theories of modified gravity and reconstruction schemes of cosmological models." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/133375.

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En esta memoria de tesis se expone el trabajo llevado a cabo por el doctorando durante los últimos cuatro años, el cual versa principalmente sobre diversos aspectos de soluciones cosmológicas obtenidas a partir de teorías de gravedad modificada. Para entender el origen y la importancia de las teorías de gravedad modificada es necesario comentar antes algunos hechos acontecidos durante el siglo XX en el marco de la cosmología. La cosmología como ciencia nació gracias a la Teoría de la Relatividad General de Albert Einstein. Antes de ésta, el espacio no era más que el lugar en el que las estrel

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47

Pützfeld, Dirk. "Building and testing cosmological models: from Friedmann to Weyl-Cartan." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968658032.

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48

Appleby, Stephen Andrew. "A study of the cosmological evolution of modified gravity models." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498785.

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Recent observations arising from a number of sources suggest that the Universe is currently undergoing a period accelerated expansion. The standard approach to modeling this behaviour is to introduce a new component total energy density of the Universe. This so called dark energy drives the accelerated expansion by virtue of having negative pressure. To date, there exists no compelling explanation as to the physical nature of dark energy. Various models exist, however they are typically plagued by fine tuning issues and unnanaturally suppressed couplings to the Standard Model. An alternative e

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49

Gregoris, Daniele. "Cosmological models, nonideal fluids and viscous forces in general relativity." Doctoral thesis, Stockholms universitet, Fysikum, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-107130.

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This thesis addresses the open questions of providing a cosmological model describing an accelerated expanding Universe without violating the energy conditions or a model that contributes to the physical interpretation of the dark energy. The former case is analyzed considering a closed model based on a regular lattice of black holes using the Einstein equation in vacuum. In the latter case I will connect the dark energy to the Shan-Chen equation of state. A comparison between these two proposals is then discussed. As a complementary topic I will discuss the motion of test particles in a gener

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50

Melia, Fulvio, Jun-Jie Wei, and Xue-Feng Wu. "A COMPARISON OF COSMOLOGICAL MODELS USING STRONG GRAVITATIONAL LENSING GALAXIES." IOP PUBLISHING LTD, 2014. http://hdl.handle.net/10150/614768.

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Strongly gravitationally lensed quasar-galaxy systems allow us to compare competing cosmologies as long as one can be reasonably sure of the mass distribution within the intervening lens. In this paper, we assemble a catalog of 69 such systems from the Sloan Lens ACS and Lens Structure and Dynamics surveys suitable for this analysis, and carry out a one-on-one comparison between the standard model, $\Lambda$CDM, and the $R_{\rm h}=ct$ Universe, which has thus far been favored by the application of model selection tools to other kinds of data. We find that both models account for the l

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