Cosmic Magnetism In Modified Theories Of Gravity
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Cosmic Magnetism In Modified Theories Of Gravity
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Author : Luiz Garcia de Andrade
language : en
Publisher:
Release Date : 2017
Cosmic Magnetism In Modified Theories Of Gravity written by Luiz Garcia de Andrade and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Unified Cosmic History In Modified Gravity From F R Theory To Lorentz Non Invariant Models
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Author : Shin'ichi Nojiri
language : en
Publisher:
Release Date : 2011
Unified Cosmic History In Modified Gravity From F R Theory To Lorentz Non Invariant Models written by Shin'ichi Nojiri and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Unified Cosmic History In Modified Gravity
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Author : Shin'ichi Nojiri
language : en
Publisher:
Release Date : 2011
Unified Cosmic History In Modified Gravity written by Shin'ichi Nojiri and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Studies Into The Nature Of Cosmic Acceleration
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Author : Jason Nicholas Dossett
language : en
Publisher:
Release Date : 2013
Studies Into The Nature Of Cosmic Acceleration written by Jason Nicholas Dossett and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Cosmology categories.
Since its discovery more than a decade ago, the problem of cosmic acceleration has become one of the largest in cosmology and physics as a whole. An unknown dark energy component of the universe is often invoked to explain this observation. Mathematically, this works because inserting a cosmic fluid with a negative equation of state into Einstein's equations provides an accelerated expansion. There are, however, alternative explanations for the observed cosmic acceleration. Perhaps the most promising of the alternatives is that, on the very largest cosmological scales, general relativity needs to be extended or a new, modified gravity theory must be used. Indeed, many modified gravity models are not only able to replicate the observed accelerated expansion without dark energy, but are also more compatible with a unified theory of physics. Thus it is the goal of this dissertation to develop and study robust tests that will be able to distinguish between these alternative theories of gravity and the need for a dark energy component of the universe. We will study multiple approaches using the growth history of large-scale structure in the universe as a way to accomplish this task. These approaches include studying what is known as the growth index parameter, a parameter that describes the logarithmic growth rate of structure in the universe, which describes the rate of formation of clusters and superclusters of galaxies over the entire age of the universe. We will explore the effectiveness of this parameter to distinguish between general relativity and modifications to gravity physics given realistic expectations of results from future experiments. Next, we will explore the modified growth formalism wherein deviations from the growth expected in general relativity are parameterized via changes to the growth equations, i.e. the perturbed Einstein's equations. We will also explore the impact of spatial curvature on these tests. Finally, we will study how dark energy with some unusual properties will affect the conclusiveness of these tests.
Generalized Perturbations In Modified Gravity And Dark Energy
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Author : Jonathan Pearson
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-09-20
Generalized Perturbations In Modified Gravity And Dark Energy written by Jonathan Pearson and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-09-20 with Science categories.
When predictions of Einstein's theory of General Relativity are compared against observations of our Universe, a huge inconsistency is found. The most popular fix for this inconsistency is to "invent" around 94% of the content of the universe: dark matter and dark energy. The dark energy is some exotic substance responsible for the apparent observed acceleration of the Universe. Another fix is to modify the theory of gravity: it is entirely plausible that Einstein's theory of General Relativity breaks down on cosmological scales, just as Newton's theory of gravity breaks down in the extreme gravitational field of the Sun. There are many alternative theories of gravity, each with the aim of describing observations of our Universe where General Relativity fails. Whether it is dark energy or some modified theory of gravity, it is clear that there is some "dark sector" in the Universe. In this thesis the author constructs a unifying framework for understanding the observational impact of general classes of dark sector theories, by formulating equations of state for the dark sector perturbations.
Modified Gravity And Cosmology On The Largest Scales
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Author : Alexandra Eileen Terrana
language : en
Publisher:
Release Date : 2017
Modified Gravity And Cosmology On The Largest Scales written by Alexandra Eileen Terrana and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
This dissertation presents a series of my contributions to research in theoretical cosmology, focusing on aspects of the very large scale universe, particularly dark energy, cosmic acceleration, modified gravity, and cosmic variance. Following an overview of the current understanding of the standard cosmological model in chapter 1, three pertinent topics are discussed in detail. A common theme among all chapters is the desire to explain the properties of the universe on the largest scales. One of the biggest mysteries on large scales is the need for dark energy to explain the observed accelerated expansion of the late universe. The unsatisfying explanation offered by the standard cosmological model and the associated enormous fine tuning problem have driven considerable interest in infrared (long-distance) modifications of general relativity. In this work, we consider a particularly well motivated modified theory, massive gravity, in which the modification is to simply assume that the particle mediating the gravitational force has a non-zero mass. For a mass on the order of the Hubble constant, this theory offers an alternative explanation of the accelerated cosmic expansion. Chapter 2 lays the theoretical groundwork for massive gravity, summarizing its history and formalism. A fundamental challenge for any modified gravity theory is sequestering the modification to large enough distance scales, so that the predictions match general relativity on solar system scales where it has been tested to high precision. Chapter 3 provides a detailed analysis of massive gravity's ability to screen its extra degrees of freedom, allowing for continuity with general relativity on short distance scales. Further, in chapter 4, we explore the cosmological production and propagation of gravitational waves in an extension of massive gravity, bigravity, determining whether there may be any testable deviations from general relativity. Understanding these predictions is crucial, as there is now a vigorous observational program to probe possible deviations from our standard model. As rapid progress in observational cosmology unfolds, not only is it paramount to construct viable modified gravity theories to test against general relativity, it is necessary to explore which observational methods will be the most powerful for constraining them. This dissertation contains progress on both of these fronts: analyzing potential modified gravity theories, and analyzing potential novel observational probes of the large scale universe. Chapter 5 provides the theoretical framework for one such novel probe, the large scale kinetic Sunyaev-Zeldovich effect. This effect is particularly intriguing because of its ability to overcome cosmic variance, and thus help us unlock the secrets of the universe on the largest scales.
Studies On Gravitational Field Equations And Important Results Of Relativistic Cosmology
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Author : Dr. Amit Prakash
language : en
Publisher: Lulu.com
Release Date :
Studies On Gravitational Field Equations And Important Results Of Relativistic Cosmology written by Dr. Amit Prakash and has been published by Lulu.com this book supported file pdf, txt, epub, kindle and other format this book has been release on with categories.
Everything About Gravity Proceedings Of The Second Lecospa International Symposium
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Author : Pisin Chen
language : en
Publisher: World Scientific
Release Date : 2016-12-29
Everything About Gravity Proceedings Of The Second Lecospa International Symposium written by Pisin Chen and has been published by World Scientific this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-12-29 with Science categories.
The proceedings of the 2nd LeCosPA International Symposium, 'Everything about Gravity', collects 78 papers contributed by the symposium's Plenary Session and Parallel Session speakers. Organizers of the Parallel Sessions have in addition prepared summaries for their own sessions. The topics range from quasi-local energy in GR in the presence of gravitational radiations, a gauge theory perspective of gravity, naked black hole firewalls related to the black hole information loss paradox, a new theory of spacetime quantization, relations between the Schwinger effect and the Hawking radiation and Unruh effect, conformal frames in cosmology, surprises in nonrelativistic naturalness, inflation and tensor fluctuations, emergent spacetime for quantum gravity, understanding strongly coupled magnetism through holographic principle, the detections of dark matter, ultra-high energy cosmic neutrinos and cosmic rays, etc. Last but not least, the closing remark delivered by John Ellis raised the following question: Does cosmological inflation require a modification of Einstein's gravity?After 100 years of remarkable success of Einstein's general relativity, the development of a successful quantum theory of gravity has become a major goal in physics in the 21st century. This volume serves as a valuable reference for scientists who are interested in frontier research topics of gravity.
Modified Gravity Progresses And Outlook Of Theories Numerical Techniques And Observational Tests
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Author : Baojiu Li
language : en
Publisher: World Scientific
Release Date : 2019-10-10
Modified Gravity Progresses And Outlook Of Theories Numerical Techniques And Observational Tests written by Baojiu Li and has been published by World Scientific this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-10-10 with Science categories.
Modified gravity theories have been a main focus of theoretical cosmology research in the past decade or so, and have been quickly developing into a mature research field that attracts attention, interest and effort from both theoretical and observational cosmologists. To be prepared for fully exploiting the future observational data, and to provide a guidance for people who are new to this field, it is useful to have a comprehensive review to summarise the current state of knowledge and to foresee the future developments.This book presents expert reviews on different topics in the field, which are then coordinated and organised in a self-consistent and self-contained manner. It is suitable for graduate students and researchers interested in the frontier research of gravity theories.
Modifications Of Einstein S Theory Of Gravity At Large Distances
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Author : Eleftherios Papantonopoulos
language : en
Publisher: Springer
Release Date : 2014-11-04
Modifications Of Einstein S Theory Of Gravity At Large Distances written by Eleftherios Papantonopoulos and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-11-04 with Science categories.
In the last few years modified gravity theories have been proposed as extensions of Einstein's theory of gravity. Their main motivation is to explain the latest cosmological and astrophysical data on dark energy and dark matter. The study of general relativity at small scales has already produced important results (cf e.g. LNP 863 Quantum Gravity and Quantum Cosmology) while its study at large scales is challenging because recent and upcoming observational results will provide important information on the validity of these modified theories. In this volume, various aspects of modified gravity at large scales will be discussed: high-curvature gravity theories; general scalar-tensor theories; Galileon theories and their cosmological applications; F(R) gravity theories; massive, new massive and topologically massive gravity; Chern-Simons modifications of general relativity (including holographic variants) and higher-spin gravity theories, to name but a few of the most important recent developments. Edited and authored by leading researchers in the field and cast into the form of a multi-author textbook at postgraduate level, this volume will be of benefit to all postgraduate students and newcomers from neighboring disciplines wishing to find a comprehensive guide for their future research.