Studies Into The Nature Of Cosmic Acceleration
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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.
Connecting Quarks With The Cosmos
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Author : National Research Council
language : en
Publisher: National Academies Press
Release Date : 2003-03-12
Connecting Quarks With The Cosmos written by National Research Council and has been published by National Academies Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003-03-12 with Science categories.
Advances made by physicists in understanding matter, space, and time and by astronomers in understanding the universe as a whole have closely intertwined the question being asked about the universe at its two extremesâ€"the very large and the very small. This report identifies 11 key questions that have a good chance to be answered in the next decade. It urges that a new research strategy be created that brings to bear the techniques of both astronomy and sub-atomic physics in a cross-disciplinary way to address these questions. The report presents seven recommendations to facilitate the necessary research and development coordination. These recommendations identify key priorities for future scientific projects critical for realizing these scientific opportunities.
Cosmic Acceleration
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Author : Nishant Agarwal
language : en
Publisher:
Release Date : 2011
Cosmic Acceleration written by Nishant Agarwal 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.
Our Universe has an exciting history of accelerated expansion. Following its inception in an event known as the big bang, the Universe underwent a phase of exponential expansion called inflation. Although precise observations of the cosmic microwave background (CMB) radiation and large-scale structure support the inflationary paradigm, the absence of a firm physical mechanism for inflation has led to a plethora of theoretical embarkments attempting to understand its genesis. Inflation lasted only for a fraction of a second, but observations suggest that thirteen billion years after inflation, the Universe began accelerating once again. This acceleration, which continues till date, is attributed to a mysterious component, dubbed dark energy, that fills up our Universe and accounts for almost 73% of the total energy density in the Universe. In this thesis we study and develop models of inflation and dark energy, in the light of current observations. We begin, in Chapter 1, with a detailed introduction to cosmic acceleration, and discuss various models of inflation and dark energy that have been studied in the literature in the recent years. In Chapter 2, we discuss how a hierarchy of Hubble flow parameters, extended to include the evolution of the inflationary sound speed, can be applied to compare a general, single-field inflationary action with cosmological observational data. In Chapter 3, we study the six-field dynamics of D3-brane inflation for a general scalar potential on the conifold, finding simple, universal behavior, such as a power law dependence for the probability of Ne e-folds of inflation. Subsequent chapters study modifications to the theory of gravity in an attempt to understand dark energy. In Chapter 4, we establish the dynamical attractor behavior in scalar-tensor theories of gravity, providing a powerful framework to analyze such theories, predicting common evolutionary characteristics that can be compared against cosmological constraints. Chapter 5 develops a cascading cosmology framework in order to study the cosmological implications of a sixdimensional (6D) theory of gravity. We find that cascading cosmology can indeed lead to an accelerating Universe. Finally, in Chapter 6, we study the issue of ghostlike instabilities in the cascading framework, and propose a mechanism to obtain flat brane and bulk solutions. We conclude in Chapter 7 with a discussion of the main results presented in this thesis.
The Accelerating Universe
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Author : Mario Livio
language : en
Publisher: Turner Publishing Company
Release Date : 2008-05-02
The Accelerating Universe written by Mario Livio and has been published by Turner Publishing Company this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008-05-02 with Science categories.
Advance Praise for The Accelerating Universe "The Accelerating Universe is not only an informative book about modern cosmology. It is rich storytelling and, above all, a celebration of the human mind in its quest for beauty in all things." —Alan Lightman, author of Einstein's Dreams "This is a wonderfully lucid account of the extraordinary discoveries that have made the last years a golden period for observational cosmology. But Mario Livio has not only given the reader one clear explanation after another of what astronomers are up to, he has used them to construct a provocative argument for the importance of aesthetics in the development of science and for the inseparability of science, art, and culture." —Lee Smolin, author of The Life of the Cosmos "What a pleasure to read! An exciting, simple account of the universe revealed by modern astronomy. Beautifully written, clearly presented, informed by scientific and philosophical insights." —John Bahcall, Institute for Advanced Study "A book with charm, beauty, elegance, and importance. As authoritative a journey as can be taken through modern cosmology." —Allan Sandage, Observatories of the Carnegie Institution of Washington
Energy Budget In The High Energy Universe Proceedings Of The International Workshop
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Author : Katsuhiko Sato
language : en
Publisher: World Scientific
Release Date : 2007-03-06
Energy Budget In The High Energy Universe Proceedings Of The International Workshop written by Katsuhiko Sato and has been published by World Scientific this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007-03-06 with Science categories.
The existence of materials with very high specific energies greatly exceeding the local virial temperature is best represented by cosmic rays, whose origin has long been a mystery. Recent astrophysical observations in X-ray, gamma-ray, neutrino, and high energy cosmic ray experiments, in conjunction with theoretical studies, have revealed various new aspects of the high energy universe, including promising candidates for cosmic ray acceleration sites. As each approach has its own advantages and limitations, it is expected that joint efforts by experimentalists and theorists in various related fields are essential.The contributions in this volume include observation of the universe through a wide range of techniques for detecting cosmic rays, neutrinos, X-rays and gamma-rays, as well as theoretical considerations in understanding their nature and astrophysical aspects.
Cosmic Acceleration As Quantum Gravity Phenomenology
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Author : Chanda Rosalyn Sojourner Prescod-Weinstein
language : en
Publisher:
Release Date : 2010
Cosmic Acceleration As Quantum Gravity Phenomenology written by Chanda Rosalyn Sojourner Prescod-Weinstein and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
The discovery of cosmic acceleration has prompted the need for a new understanding of cosmology. The presence of this acceleration is often described as the dark energy problem or the Lambda problem. The simplest explanation is that the acceleration is due to addition of a cosmological constant to Einstein's equation, but this resolution is unsatisfactory as it leaves several unanswered questions. Although General Relativity has been tested in the strong-field limit, the apparent dark energy may be urging us to consider experimental cosmology as such a test for large scales. In this vein, I have pursued a study of modifications to Einstein's gravity as well as possible related quantum gravity phenomenology. Not only must the details of modified gravities be worked out, but their impact on other astrophysics must be checked. For example, structure formation provides a strong test of any cosmic acceleration model because a successful dark energy model must not inhibit the development of observed large-scale structures. Traditional approaches to studies of structure formation in the presence of dark energy or a modified gravity implement the Press & Schechter formalism. I explore the potential for universality in the Press & Schechter formalism and what dark matter haloes may be able to tell us about cosmology.
From Ultra Rays To Astroparticles
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Author : Brigitte Falkenburg
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-30
From Ultra Rays To Astroparticles written by Brigitte Falkenburg 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 2012-12-30 with Science categories.
The scope of the book is to give an overview of the history of astroparticle physics, starting with the discovery of cosmic rays (Victor Hess, 1912) and its background (X-ray, radioactivity). The book focusses on the ways in which physics changes in the course of this history. The following changes run parallel, overlap, and/or interact: - Discovery of effects like X-rays, radioactivity, cosmic rays, new particles but also progress through non-discoveries (monopoles) etc. - The change of the description of nature in physics, as consequence of new theoretical questions at the beginning of the 20th century, giving rise to quantum physics, relativity, etc. - The change of experimental methods, cooperations, disciplinary divisions. With regard to the latter change, a main topic of the book is to make the specific multi-diciplinary features of astroparticle physics clear.
Study Of Accelerated Cosmic Expansion
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Author : Nisha Rani
language : en
Publisher: Mohd Abdul Sattar
Release Date : 2022-08-09
Study Of Accelerated Cosmic Expansion written by Nisha Rani and has been published by Mohd Abdul Sattar this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-08-09 with Science categories.
Physical cosmology includes the scientific study of the origin, evolution and dynamics of the universe. Due to impressive progress both on the theoretical and observational side, scientists are able to resolve many of the puzzles of the universe. Nevertheless, many questions are not answered completely. For instance, "What are the constituents of the universe?" and "How does the dynamics of the universe evolve?" The curiosity to get convincing answers to these questions, motivates one to work in this field. According to the hot Big Bang model, the universe started from a bang and its properties change with time. The discovery of the Cosmic Microwave Background Radiation (CMBR) by Penzias and Wilson in 1965 was important in making the Big Bang model the accepted model of the universe [5]. A landmark discovery in 1998 by two groups working independently on Supernovae Ia was instrumental in changing the way we understand our universe. They found that the expansion of the universe is accelerating [6, 7]. To explain the accelerated expansion of the universe, various models have been proposed. The most widely accepted one is the Lambda Cold Dark Matter (ΛCDM) model [8]. According to this model, the universe is flat and is expanding at an accelerated rate. It is composed of baryonic matter, dark matter and dark energy. Dark energy is the name given to the cause of the cosmic acceleration.
Astrophysics At Ultra High Energies
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Author : Maurice Mandel Shapiro
language : en
Publisher: World Scientific
Release Date : 2007
Astrophysics At Ultra High Energies written by Maurice Mandel Shapiro and has been published by World Scientific this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Science categories.
This book introduces young researchers to the exciting field of ultra-high energy astrophysics including charged particles, gamma rays and neutrinos. At ultra-high energy the radiation is produced by interactions of cosmic ray particles accelerated in explosive events such as supernovae or hypernovae, black holes or, possibly, the big bang. Through direct contact with senior scientists, now actively planning the next generation of experiments/models, the excitement and motivation for research at ultra-high energy was conveyed. The underpinning of these fields is a synthesis of knowledge and techniques from nuclear and particle physics, astronomy and cosmology. Informing the participants of this background, how it was derived, and the new challenges for the future are the major goal. Further, the course has helped to foster new astrophysical research and promoted contacts, which have resulted in new collaborations. Sample Chapter(s). Chapter 1: Gamma-Ray Burst: Discoveries With Swift (352 KB). Contents: Powerful Astrophysical Sources: Gamma Ray Bursts: Discoveries with Swift (A Wells); Gamma Ray Burst Phenomenology in the Swift Era (P M(r)sziros); The Nature of Dark Matter (P L Biermann & F Munyaneza); Cosmic Rays: Particle Acceleration and Propagation in the Galaxy (V S Ptuskin); GRB as Sources of Ultra-High Energy Particles (P M(r)sziros); The KASCADE-Grande Experiment (F Cossavela et al.); Gamma Ray and Neutrino Astronomy: Study of Galactic Gamma Ray Sources with Milagro (J Goodman); The GLAST Mission and Observability of Supernovae Remnants (O Tibolla); First Results from AMANDA using TWR System (A Silvestri); and other papers. Readership: Academics in astrophysics, high energy, cosmology and earth science."
Particle Acceleration In Cosmic Plasmas
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Author : André Balogh
language : en
Publisher: Springer
Release Date : 2015-06-25
Particle Acceleration In Cosmic Plasmas written by André Balogh and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-06-25 with Science categories.
The review articles collected in this volume present a critical assessment of particle acceleration mechanisms and observations from suprathermal particles in the magnetosphere and heliosphere to high-energy cosmic rays, thus covering a range of energies over seventeen orders of magnitude, from 103 eV to 1020 eV. The main themes are observations of accelerated populations from the magnetosphere to extragalactic scales and assessments of the physical processes underlying particle acceleration in different environments (magnetospheres, the solar atmosphere, the heliosphere, supernova remnants, pulsar wind nebulae and relativistic outflows). Several contributions review the status of shock acceleration in different environments and also the role of turbulence in particle acceleration. Observational results are compared with modelling in different parameter regimes. The book concludes with contributions on the status of particle acceleration research and its future perspectives. This volume is aimed at graduate students and researchers active in astrophysics and space science. Previously published in Space Science Reviews journal, Vol. 173 Nos. 1-4, 2012.