Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 98 for “"Dark Energy"”.
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Rendering dark energy void
… very large scales. Further assuming flatness and dark energy in the form of Einstein's cosmological constant A then implies that the latter contributes roughly 73% of the total energy of the universe, cold dark matter (CD'I) 23SiC, and baryons, the matter we are made, only 4%.
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Simulations of dark energy cosmologies
… growth of cosmic structure in different dark energy models, using ultra-large volume N-body simulations. We measure key observables such as the growth of large scale structure, the halo mass function and baryonic acoustic oscillations. We study the power spectrum in redshift space in …
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Observational aspects of dark energy
… the presence of a cosmological constant and cold dark matter along with usual components. Additionally, it requires a special set of initial conditions, such as those that can be generated by inflation. The $\Lambda$CDM model is consistent with all current data and most model parameters are known …
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Dark energy and CMB anisotropy
… We propose a scalar field model of the dark energy as a mechanism for suppressing low l multipoles through late-Universe evolution of metric fluctuations and the integrated Sachs-Wolfe (ISW) effect. We find that for a constant dark energy equation of state, theoretical predictions …
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Challenges in the hunt for dark energy dynamics
… the observed acceleration of the Universe. The 'dark energy' believed to supply the negative pressure responsible for this cosmic acceleration remains elusive despite over a decade of investigation. Hunting for deviation from the 'vanilla' cosmological model, ACDM, and detecting dynamics with …
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Constraining dark energy using real and mock galaxy surveys
In this thesis, we study how dark energy may be constrained by measurements of large-scale clustering in future galaxy surveys, and through the imprint of a time-varying large-scale potential on the CMB (the integrated Sachs-Wolfe effect). We use semi-analytical galaxy formation models implemented …
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Topics in cosmology: structure formation, dark energy and recombination
… in finding the accretion and merger history of dark matter halos. Dark matter halos are the collapsed dark matter structures in the late time evolution of the universe, whose existence is vital for the formation of galaxies in the Universe as they act as the potential wells where normal matter …
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Single-Fluid Approach to Modeling Dark Matter and Dark Energy
… overwhelming evidence for the ex istence of dark energy, a mysterious and dominant component responsible for the accelerated expan sion of the universe. The nature of dark energy remains one of the most intriguing puzzles in modern cosmology. This dissertation presents a comprehensive …
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Cosmological backreaction : from the local Hubble expansion rate to dark energy
… of the Universe, caused by the mysterious dark energy is currently the most severe crisis in cosmology, even in physics. In this dissertation, we argue that light may be shed on this crisis by means of the cosmological backreaction mechanism in the averaging problem in inhomogeneous and …
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Testing New Weak Lensing Measurement Techniques With The Dark Energy Survey
… of wind at the Blanco Telescope, the home of the Dark Energy Camera (DECam), on Dark Energy Survey (DES) image quality. We find it to have a likely negligible impact on the weak gravitational lensing measurements conducted with images taken during high wind. We then present the methods and …
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The Search for the Highest Redshift Quasars using the Dark Energy Survey
… quasars using new multi wavelength data from the Dark Energy Survey, the VISTA Hemisphere Survey and Wide-Field Infrared Survey Explorer. The beginning of the thesis focusses on developing an automated selection code for z > 6 quasars, including the automatic rejection of foreground contaminating …
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Spherically symmetric dark energy structures in the context of Chaplygin gas model
… the existence of spherically symmetrical dark energy structures under the context of Chaplygin gas. A scaling solution of the form r -2/3 is found for the density and then we calculated the corresponding rotational curve and it turns out to be unrealistic implying that such objects don't …
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Theoretical and experimental approaches to the dark energy and the cosmological constant problem.
… the expansion of the universe with no need for dark energy. Renormalizability of the theory is studied as well. It is also shown that, under a certain condition, the theory is power-counting renormalizable. Supersymmetry provides an alternative solution to the cosmological problem as well. The …
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GALAXY-HALO CONNECTION AND CLUSTERING IN THE PRESENCE OF DYNAMICAL DARK ENERGY AND MASSIVE NEUTRINOS
… on the modelling of the connection between dark matter subhaloes and galaxies, and the analysis of the galaxy cluster mass function and clustering, in cosmologies alternative to the standard LCDM model. To this aim a large set of cosmological N-body simulations has been used, the so-called …
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Computational Bayesian techniques applied to cosmology
This thesis presents work around 3 themes: dark energy, gravitational waves and Bayesian inference. Both dark energy and gravitational wave physics are not yet well constrained. They present interesting challenges for Bayesian inference, which attempts to quantify our knowledge of the universe …
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The distribution of dark matter at large scales and in gravitational lenses
The nature of dark matter and dark energy is one of the most important unsolved problems in cosmology. The distribution of dark matter at cosmological scales, galactic scales and subgalactic scales all reveal complementary aspects of the physics of dark matter. The broadest set of probes for dark …
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A study of chameleon-photon mixing from pulsars
A number of solutions to the dark energy problem have been proposed in literature, the simplest is the cosmological constant A. The cosmological constant lacks theoretical explanation for its extremely small value, thus dark energy is more generally modelled as a quintessence scalar field rolling …
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Testing General Relativity with the next generation of cosmological surveys
… physics (cosmological problem) dubbed dark energy (DE) problem. In general relativity (GR) framework view point, there are two ways to explain where this acceleration might originate from; this riddle might either emerge from some unknown dark energy models or general relativity is a …
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