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Made available in DSpace on 2014-06-11T19:32:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-09-02Bitstream added on 2014-06-13T21:03:29Z : No. of bitstreams: 1 sobreira_f_dr_ift.pdf: 3580340 bytes, checksum: 5b2c8fe81dd5d4ebcb30572e1f260ebc (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nesta tese estudamos previsões sobre os erros nos parâmetros cosmológicos usando a forma integral da função de correlação angular de dois pontos em diferentes cenários para o projeto Dark Energy Survey. O modelo adotado tem 26 parâmetros e inclui efeitos de distorção no redshift, erros gaussianos de redshift fotométrico, viés da distribuição de galáxias e matéria escura e não-linearidade no espectro de potência. A matriz de Fisher foi construída usando a matriz de covariância considerando a correlação entre diferentes faixas de redshift. Mostramos que, sobre alguma hipóteses, o Dark Energy Survey será capaz de vincular o parâmetro da equação de estado de energia escura w e o parâmetro da densidade de matéria escura fria 'Ω IND cdm' com incerteza de 21% e 13% respectivamente. Quando combinamos informações de outras observações a precisão na determinação destes parâmetros aumenta para 11% e 4% respectivamente / In this thesis, we study forecasts of cosmological parameters from the upcoming Dark Energy Survey project obtained using the full shape 2-point angular correlation function in different scenarios. The angular correlation function model adopted has 26 parameters and includes the effects of linear redshift space distortion, photometric redshift gaussian errors, galaxy bias and non-linearities in the power spectrum. The Fisher information matrix is constructed with the full covariance matrix, which takes into account the correlation between nearby redshift shells arising from the photometric redshift error. We show that under some resonable assumptions the Dark Energy Survey should be able to constrain the dark energy equation of estate parameter w and the cold dark matter density 'Ω IND cdm' with a precision of the order of 21% and 13% respectively from the full shape of the angular correlation function alone. When combined with priors from other observations the precision in the determination of these parameters increase to 11% and 4% respectively

Currently one of the most exciting problems in cosmology is the nature of dark energy, which is responsible for the late time accelerated expansion of the universe. Dark energy modifies the distance-redshift relation, and governs the late time evolution of gravitational potentials in the universe. Therefore by observing large scale structure we can gain valuable information on the nature of dark energy. In this thesis we examine a particular theory of dark energy, known as elastic dark energy. Using weak lensing and the ISW effect, coupled with CMB and SNIa data, we find lower bounds for the sound speed of elastic dark energy. We also explore how this model behaves in the presence of collapsing matter.

Yeung, Shek = 暗能量和暗物質模型課題 / 楊碩. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (p. 88-91). / Abstracts in English and Chinese. / Yeung, Shek = An neng liang he an wu zhi mo xing ke ti / Yang Shuo. / Chapter 1 --- Overview of Cosmology --- p.1 / Chapter 1.1 --- The Friedmann-Robertson-Walker Metric and the Friedmann Equations --- p.1 / Chapter 1.2 --- The Hubble constant and the Expansion of the Universe --- p.3 / Chapter 1.3 --- The Energy Contents in the Universe --- p.4 / Chapter 1.4 --- Cosmological Observations --- p.8 / Chapter 2 --- Review of CMB Physics --- p.13 / Chapter 2.1 --- The Anisotropy Spectrum --- p.13 / Chapter 2.2 --- The Boltzmann Equations and Einstein Field Equation --- p.15 / Chapter 2.3 --- Initial Conditions --- p.18 / Chapter 2.4 --- Inhomogeneities of Matters --- p.21 / Chapter 2.5 --- Inhomogeneities and Anisotropies of Photons --- p.23 / Chapter 2.5.1 --- Tightly Coupled Limit of the Boltzmann equations --- p.23 / Chapter 2.5.2 --- Diffusion Damping --- p.25 / Chapter 2.5.3 --- Free Streaming --- p.25 / Chapter 2.5.4 --- Cosmological Parameters --- p.26 / Chapter 3 --- Extra Dimension Model with Casimir Effect --- p.28 / Chapter 3.1 --- Introduction --- p.28 / Chapter 3.2 --- Extra Dimension Model --- p.29 / Chapter 3.3 --- The Casimir Effect --- p.34 / Chapter 3.4 --- Results and Conclusion --- p.40 / Chapter 4 --- Decaying Sterile Neutrino Model --- p.44 / Chapter 4.1 --- Introduction --- p.44 / Chapter 4.2 --- The Model --- p.46 / Chapter 4.3 --- Results and Conclusion --- p.61 / Chapter 5 --- Summary of the Thesis --- p.86 / Bibliography --- p.88

Chan, Wing Hang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 76-78). / Abstracts in English and Chinese. / Chan, Wing Hang. / Chapter 1 --- Review of Cosmology --- p.1 / Chapter 1.1 --- Background Evolution of Universe --- p.1 / Chapter 1.1.1 --- The Cosmological Principle --- p.1 / Chapter 1.1.2 --- The Non-static Universe --- p.3 / Chapter 1.1.3 --- Robertson-Walker metric --- p.3 / Chapter 1.1.4 --- Scale Factor and Cosmological Redshift --- p.3 / Chapter 1.1.5 --- Hubble Constant --- p.4 / Chapter 1.1.6 --- The Einstein Field Equations --- p.4 / Chapter 1.1.7 --- The Cosmological Constant --- p.6 / Chapter 1.1.8 --- Time Evolution --- p.6 / Chapter 1.1.9 --- Continuity Equation --- p.7 / Chapter 1.1.10 --- Conformal Distance --- p.8 / Chapter 1.2 --- Observational Data --- p.8 / Chapter 1.2.1 --- Type Ia Supernovae --- p.9 / Chapter 1.2.2 --- Cosmic Microwave Background --- p.9 / Chapter 2 --- Review of Dark Energy Models --- p.11 / Chapter 2.1 --- The Cosmological Constant --- p.11 / Chapter 2.2 --- Quintessence --- p.11 / Chapter 2.3 --- Extra Dimension Models --- p.12 / Chapter 2.3.1 --- Kaluza-Klein --- p.12 / Chapter 2.3.2 --- Generalized Homogeneous and Isotropic Extra Dimensions --- p.12 / Chapter 3 --- Review of CMB and Type Ia Supernovae --- p.17 / Chapter 3.1 --- Type Ia Supernovae --- p.17 / Chapter 3.1.1 --- Comparison of cosmological models with recent SNIa data --- p.18 / Chapter 3.2 --- Cosmic Microwave Background Radiation --- p.18 / Chapter 3.2.1 --- Power Spectrum of CMBA --- p.18 / Chapter 3.2.2 --- Photon Baryon Oscillation --- p.21 / Chapter 3.2.3 --- Acoustic Peaks --- p.23 / Chapter 3.2.4 --- Matter Perturbation --- p.24 / Chapter 3.2.5 --- Baryon Loading --- p.24 / Chapter 3.2.6 --- Photons Driving --- p.25 / Chapter 3.2.7 --- Initial Conditions --- p.25 / Chapter 3.2.8 --- Reionization --- p.26 / Chapter 3.2.9 --- The Vanilla ACDM Model --- p.26 / Chapter 3.2.10 --- Summary of CMBA --- p.26 / Chapter 4 --- Constraining Dark Energy Models --- p.27 / Chapter 4.1 --- Constraining Dark Energy Density Using SN Ia data --- p.27 / Chapter 4.1.1 --- Direct Calculation of Dark Energy Density --- p.27 / Chapter 4.2 --- Constraining Dark Energy Density Using CMB data --- p.31 / Chapter 4.2.1 --- Dark Energy Evolution for time varying EOS --- p.31 / Chapter 4.2.2 --- Dark Energy Density Perturbation --- p.32 / Chapter 4.2.3 --- Parameterization of Time Varying Dark Energy --- p.32 / Chapter 4.2.4 --- Effect of Dark Energy Density on CMBA power spectrum --- p.33 / Chapter 4.2.5 --- Limitations and Difficulties Constraining Dark Energy Equation of State --- p.41 / Chapter 4.2.6 --- Constraining the Evolution of Dark Energy Density with a polynomial model --- p.54 / Chapter 4.2.7 --- Constraining Evolution of Dark Energy Density with Gaussian-type EOS --- p.59 / Chapter 4.2.8 --- Constraining Evolution of Dark Energy Step Function EOS with CMB Acoustic Peaks --- p.66 / Chapter 5 --- Summary --- p.73 / Bibliography --- p.76

The most popular way to achieve accelerated expansion of the universe is by introducing a scalar field in which motion of state varies with time. The accelerated expanded universe was first observed by Type Ia supernovae and future confirmed by the latest of CMB (Cosmic Microwave Background). The reason for the accelerated universe is the existence of dark energy. In this dissertation, we discuss the relationship between dark matter, dark energy, reheating and the standard model, and we find that it is possible for us to unify dark energy, dark matter and a reheating field into one scalar field. There is a very important stage called inflationary, and we find that the residue of the inflationary field, which is also described by a scalar field, can form bubbles in our universe due to the gravity force. We discuss that these bubbles are stable since they are trapped in their potential wells, and the bubbles can be a candidate for dark matter. We also discuss the scalar singlet filed, with the simplest interaction with the Higgs field, and we find that a static, classical droplet can be formed. The physics picture of the droplet is natural, and it is almost the same as the formation of an oil droplet in water. We show that the droplet is absolutely stable. Due to the very weak interaction with the Standard Model particles, the droplet becomes a very promising candidate for dark matter.

The most popular way to achieve accelerated expansion of the universe is by introducing a scalar field in which motion of state varies with time. The accelerated expanded universe was first observed by Type Ia supernovae and future confirmed by the latest of CMB (Cosmic Microwave Background). The reason for the accelerated universe is the existence of dark energy. In this dissertation, we discuss the relationship between dark matter, dark energy, reheating and the standard model, and we find that it is possible for us to unify dark energy, dark matter and a reheating field into one scalar field. There is a very important stage called inflationary, and we find that the residue of the inflationary field, which is also described by a scalar field, can form bubbles in our universe due to the gravity force. We discuss that these bubbles are stable since they are trapped in their potential wells, and the bubbles can be a candidate for dark matter. We also discuss the scalar singlet filed, with the simplest interaction with the Higgs field, and we find that a static, classical droplet can be formed. The physics picture of the droplet is natural, and it is almost the same as the formation of an oil droplet in water. We show that the droplet is absolutely stable. Due to the very weak interaction with the Standard Model particles, the droplet becomes a very promising candidate for dark matter.

Thesis (Ph. D.)--University of Chicago, Dept. of Physics, December 2003. / Includes bibliographical references. Also available on the Internet.

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 order, topics discussed include the classicalization of cosmological perturbations (chapter 2), and the effects of including the dilaton and its fluctuations on a novel mechanism for the production of inhomogeneities in string gas cosmology (chapter 3). At second order, an original solution to the Dark Energy problem is proposed (chapter 4), and the effects of back-reaction on the power spectrum, including the spectral index and the gaussianity, are examined (chapter 5).

Thesis (Ph.D.)--Brown University, 2005. / Vita. Thesis advisor: David Lowe. Includes bibliographical references (leaves 111-122). Also available online.