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Investigating Inhomogeneous Szekeres Models And Their Applications To Precision Cosmology
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Book Synopsis Investigating Inhomogeneous Szekeres Models and Their Applications to Precision Cosmology by : Austin Chandler Peel
Download or read book Investigating Inhomogeneous Szekeres Models and Their Applications to Precision Cosmology written by Austin Chandler Peel and published by . This book was released on 2015 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Exact solutions of Einstein's field equations that can describe the evolution of complex structures in the universe provide complementary frameworks to standard perturbation theory in which to analyze cosmological and astrophysical phenomena. The flexibility and generality of the inhomogeneous and anisotropic Szekeres metric make it the best known exact solution to explore nonlinearities in the universe. We study applications of Szekeres models to precision cosmology, focusing on the influence of inhomogeneities in two primary contexts--the growth rate of cosmic structures and biases in distance determinations to remote sources. We first define and derive evolution equations for a Szekeres density contrast, which quantifies exact deviations from a smooth background cosmology. Solving these equations and comparing to the usual perturbative approach, we find that for models with the same matter content, the Szekeres growth rate is larger through the matter-dominated cosmic era. Including a cosmological constant, we consider exact global perturbations, as well as the evolution of a single extended structure surrounded by an almost homogeneous background. For the former, we use growth data to obtain a best fit Szekeres model and find that it can fit the data as well as the standard Lambda-Cold Dark Matter (LCDM) cosmological model but with different cosmological parameters. Next, to study effects of inhomogeneities on distance measures, we build an exact relativistic Swiss-cheese model of the universe, where a large number of non-symmetric and randomly placed Szekeres structures are embedded within a LCDM background. Solving the full relativistic propagation equations, light beams are traced through the model, where they traverse the inhomogeneous structures in a way that mimics the paths of real light beams in the universe. For beams crossing a single structure, their magnification or demagnification reflects primarily the net density encountered along the path. Despite nontrivial evolution and density distributions of the structures, the effect of tidal shearing on the beams remains small. Finally, we study source magnification probability distributions for various redshifts, finding a limitation of the models in that the distributions do not consistently resemble those of gravitational lensing analyses in cosmological simulations.
Book Synopsis Cosmological Observables in the Quasi-spherical Szekeres Model by : Robert G. Buckley
Download or read book Cosmological Observables in the Quasi-spherical Szekeres Model written by Robert G. Buckley and published by . This book was released on 2014 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: The standard model of cosmology presents a homogeneous universe, and we interpret cosmological data through this framework. However, structure growth creates nonlinear inhomogeneities that may affect observations, and even larger structures may be hidden by our limited vantage point and small number of independent observations. As we determine the universe's parameters with increasing precision, the accuracy is contingent on our understanding of the effects of such structures. For instance, giant void models can explain some observations without dark energy. Because perturbation theory cannot adequately describe nonlinear inhomogeneities, exact solutions to the equations of general relativity are important for these questions. The most general known solution capable of describing inhomogeneous matter distributions is the Szekeres class of models. In this work, we study the quasi-spherical subclass of these models, using numerical simulations to calculate the inhomogeneities' effects on observations. We calculate the large-angle CMB in giant void models and compare with simpler, symmetric void models that have previously been found inadequate to matchobservations. We extend this by considering models with early-time inhomogeneities as well. Then, we study distance observations, including selection effects, in models which are homogeneous on scales around 100 Mpc--consistent with standard cosmology--but inhomogeneous on smaller scales. Finally, we consider photon polarizations, and show that they are not directly affected by inhomogeneities. Overall, we find that while Szekeres models have some advantages over simpler models, they are still seriously limited in their ability to alter our parameter estimation while remaining within the bounds of current observations.
Book Synopsis Investigating Cosmological Distances as a Function of the Red-shift in the Szekeres Inhomogeneous Cosmological Models by : Anthony Chukwuemeka Nwankwo
Download or read book Investigating Cosmological Distances as a Function of the Red-shift in the Szekeres Inhomogeneous Cosmological Models written by Anthony Chukwuemeka Nwankwo and published by . This book was released on 2011 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: The interpretation of cosmological observations depends on the choice of a cosmological model. One must choose a cosmological model, calculate the observables in the chosen cosmological model and then confront the results of the calculations with the data. Cosmological observations are made on the past null cone, which involve observation of luminosities and red-shifts of astrophysical objects like distant supernovae in the universe. The physical characteristics of these observed objects such as the red-shift and the magnitudes are dependent on the space-time in which they travelled through to reach the observer, and thus choosing the correct model of the universe is of crucial importance in the interpretation of cosmological observations. The universe has been observed to be inhomogeneous on scales that can affect observed quantities such as area distance, luminosity distance and red-shift. Because of this, it is necessary to use cosmological models that can take into account the observed inhomogeneities to study the universe such as the Szekeres inhomogeneous models and computing observable quantities in the Szekeres model is a non-trivial problem, more specifically computing the area distance in general requires one to compute the partial derivatives of the null vector components.
Book Synopsis Structures in the Universe by Exact Methods by : Krzysztof Bolejko
Download or read book Structures in the Universe by Exact Methods written by Krzysztof Bolejko and published by Cambridge University Press. This book was released on 2010 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reviews developments in applications of inhomogeneous models to cosmology, for graduate students and academic researchers in astrophysics.
Book Synopsis Inhomogeneous Cosmological Models by : Andrzej Krasinski
Download or read book Inhomogeneous Cosmological Models written by Andrzej Krasinski and published by Cambridge University Press. This book was released on 2006-11-02 with total page 335 pages. Available in PDF, EPUB and Kindle. Book excerpt: Digitally printed first paperback version (with corrections)
Book Synopsis Inhomogeneous Cosmological Models - Proceedings Of The Spanish Relativity Meeting by : J M M Senovilla
Download or read book Inhomogeneous Cosmological Models - Proceedings Of The Spanish Relativity Meeting written by J M M Senovilla and published by World Scientific. This book was released on 1995-08-31 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is devoted mainly to one of the more relevant subjects of the last two decades, namely, Inhomogeneous Cosmological Models. This subject has undergone a remarkable advance during the last decade, and the achievements attained have been quite numerous both from the observational and the theoretical point of view.
Book Synopsis Some Mathematical Problems in Inhomogeneous Cosmology by : Chris Oliwa
Download or read book Some Mathematical Problems in Inhomogeneous Cosmology written by Chris Oliwa and published by . This book was released on 2001 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Class of Inhomogeneous Cosmological Models by : P. Szekeres
Download or read book A Class of Inhomogeneous Cosmological Models written by P. Szekeres and published by . This book was released on 1974 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Studies Into the Averaging Problem by : Tharake S. Wijenayake
Download or read book Studies Into the Averaging Problem written by Tharake S. Wijenayake and published by . This book was released on 2016 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the tremendous improvement in the precision of available astrophysical data in the recent past, it becomes increasingly important to examine some of the underlying assumptions behind the standard model of cosmology and take into consideration nonlinear and relativistic corrections which may affect it at percent precision level. Due to its mathematical rigor and fully covariant and exact nature, Zalaletdinov's macroscopic gravity (MG) is arguably one of the most promising frameworks to explore nonlinearities due to inhomogeneities in the real Universe. We study the application of MG to precision cosmology, focusing on developing a self-consistent cosmology model built on the averaging framework that adequately describes the large-scale Universe and can be used to study real data sets. We first implement an algorithmic procedure using computer algebra systems to explore new exact solutions to the MG field equations. After validating the process with an existing isotropic solution, we derive a new homogeneous, anisotropic and exact solution. Next, we use the simplest (and currently only) solvable homogeneous and isotropic model of MG and obtain an observable function for cosmological expansion using some reasonable assumptions on light propagation. We find that the principal modification to the angular diameter distance is through the change in the expansion history. We then linearize the MG field equations and derive a framework that contains large-scale structure, but the small scale inhomogeneities have been smoothed out and encapsulated into an additional cosmological parameter representing the averaging effect. We derive an expression for the evolution of the density contrast and peculiar velocities and integrate them to study the growth rate of large-scale structure. We find that increasing the magnitude of the averaging term leads to enhanced growth at late times. Thus, for the same matter content, the growth rate of large scale structure in the MG model is stronger than that of the standard model. Finally, we constrain the MG model using Cosmic Microwave Background temperature anisotropy data, the distance to supernovae data, the galaxy power spectrum, the weak lensing tomography shear-shear cross-correlations and the baryonic acoustic oscillations. We find that for this model the averaging density parameter is very small and does not cause any significant shift in the other cosmological parameters. However, it can lead to increased errors on some cosmological parameters such as the Hubble constant and the amplitude of the linear matter spectrum at the scale of 8h-1Mpc. Further studies are needed to explore other solutions and models of MG as well as their effects on precision cosmology.
Book Synopsis Structures in the Universe by Exact Methods by : Krzysztof Bolejko
Download or read book Structures in the Universe by Exact Methods written by Krzysztof Bolejko and published by Cambridge University Press. This book was released on 2009-10-22 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the structures in our Universe are mapped out on ever larger scales, and with increasing detail, the use of inhomogeneous models is becoming an essential tool for analyzing and understanding them. This book reviews a number of important developments in the application of inhomogeneous solutions of Einstein's field equations to cosmology. It shows how inhomogeneous models can be employed to study the evolution of structures such as galaxy clusters and galaxies with central black holes, and to account for cosmological observations like supernovae dimming, the cosmic microwave background, baryon acoustic oscillations or the dependence of the Hubble parameter on redshift within classical general relativity. Whatever `dark matter' and `dark energy' turn out to be, inhomogeneities exist on many scales and need to be investigated with all appropriate methods. This book is of great value to all astrophysicists and researchers working in cosmology, from graduate students to academic researchers.
Download or read book INIS Atomindeks written by and published by . This book was released on 1980 with total page 1440 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Study of Homogeneous and Inhomogeneous Cosmological Models of the Universe by : Yaobing Deng
Download or read book Study of Homogeneous and Inhomogeneous Cosmological Models of the Universe written by Yaobing Deng and published by . This book was released on 1990 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Powerlaws, Bumps and Wiggles by : Christopher M. Orban
Download or read book Powerlaws, Bumps and Wiggles written by Christopher M. Orban and published by . This book was released on 2011 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: With the many questions raised by the discovery, about a decade ago, that the universe is in an accelerating phase of expansion, it is clear that cosmological N-body simulations will continue to play a key role in unravelling this mysterious phenomenon. Historically, the first generation of cosmological N-body codes were tested and verified using self-similar models for dark matter clustering that have special "scale-free" properties. These models, in addition to allowing novel tests of numerical accuracy, are also interesting as fundamental problems and have been insightful in illuminating the non-linear physics of cosmological structure formation. In this thesis I return to this theme, in the first part investigating in considerable detail a new class of self-similar dark matter clustering models with a large-scale clustering feature that closely resembles baryonic acoustic oscillations (BAO) - a key distance indicator for dark energy studies. The non-linear physics of this simplified model was investigated using cosmological N-body simulations and the results compared both to perturbation theory and a phenomenological model. In these comparisons the phenomenological model and one of the two perturbation theory models discussed generally matched the simulation data quite well - more specifically the "SimpleRG" perturbation theory scheme of McDonald (2007) was remarkably accurate. I also carried out (for the first time) a suite of numerical tests with this new self-similar model, concluding that with modest numerical requirements, current N-body simulations will accurately model the non-linear evolution of a BAO-like feature even for a wide range of broadband spectral power. Importantly, this statement is true of the shift of the BAO clustering feature - a crucial systematic for dark energy studies. In the second half of this thesis, again making use of self-similar numerical tests, I evaluate an alternative method for setting up and running ensembles of cosmological N-body simulations developed by Sirko (2005) based on the ideas of Pen (1997). This method maintains correspondence between the actual and simulated real-space (rather than fourier space) properties of the cosmological model and accordingly allows the average density in each box to vary slightly from one realization to another. Extensive tests show that this approach gives indistinguishable results, compared to the standard method, for the mean dark matter and halo clustering properties but that the box-to-box variance of these statistics in the new method is much higher than expected, making the scheme substantially sub-optimal for most uses. I discuss the assumptions in the method which cause this and comment on a regime where the Sirko (2005) approach may be very useful.
Book Synopsis Certain Inhomogeneous Cosmological Models by : Nazira Tomimura
Download or read book Certain Inhomogeneous Cosmological Models written by Nazira Tomimura and published by . This book was released on 1976 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Studies in Exact Solutions and Inhomogeneous Cosmological Models by : James M. Richardson
Download or read book Studies in Exact Solutions and Inhomogeneous Cosmological Models written by James M. Richardson and published by . This book was released on 2008 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Inhomogeneous Conformal Cosmological Models by : Robert Alan Campbell
Download or read book Inhomogeneous Conformal Cosmological Models written by Robert Alan Campbell and published by . This book was released on 1985 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Confronting Precision Cosmology with the Minimal Supersymmetric Standard Model by :
Download or read book Confronting Precision Cosmology with the Minimal Supersymmetric Standard Model written by and published by . This book was released on 2012 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt:
