Author: Amare Abebe
Publisher: LAP Lambert Academic Publishing
ISBN: 9783844314045
Category :
Languages : en
Pages : 100
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Book Description
This book studies the evolution of scalar cosmological perturbations in the 1+3 Covariant Gauge-Invariant formalism for generic f(R) theories of gravity. It provides with a complete set of equations describing the evolution of matter and curvature fluctuations for a multi-fluid cosmological medium. It also deals with a specific model of a radiation-dust fluid universe described by barotropic equations of state where the perturbation equations are applied around a background solution of a specific toy model of gravity and looks at exact solutions for scales much smaller and much larger than the Hubble radius.
Author: Amare Abebe Gidelew
Publisher:
ISBN:
Category :
Languages : en
Pages : 168
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Book Description
Author: Christos G. Tsagas
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Emmanuel N. Saridakis
Publisher: Springer Nature
ISBN: 3030837157
Category : Science
Languages : en
Pages : 631
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Book Description
With a focus on modified gravity this book presents a review of the recent developments in the fields of gravity and cosmology, presenting the state of the art, high-lighting the open problems, and outlining the directions of future research. General Relativity and the ΛCDM framework are currently the standard lore and constitute the concordance paradigm of cosmology. Nevertheless, long-standing open theoretical issues, as well as possible new observational ones arising from the explosive development of cosmology in the last two decades, offer the motivation and lead a large amount of research to be devoted in constructing various extensions and modifications. In this review all extended theories and scenarios are first examined under the light of theoretical consistency, and are then applied in various geometrical backgrounds, such as the cosmological and the spherical symmetric ones. Their predictions at both the background and perturbation levels, and concerning cosmology at early, intermediate and late times, are then confronted with the huge amount of observational data that astrophysics and cosmology has been able to offer in the last two decades. Theories, scenarios and models that successfully and efficiently pass the above steps are classified as viable and are candidates for the description of Nature, allowing readers to get a clear overview of the state of the art and where the field of modified gravity is likely to go. This work was performed in the framework of the COST European Action “Cosmology and Astrophysics Network for Theoretical Advances and Training Actions” - CANTATA.
Author: Jonathan Pearson
Publisher: Springer Science & Business Media
ISBN: 331901210X
Category : Science
Languages : en
Pages : 213
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Book Description
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.
Author: David Vasak
Publisher: Springer Nature
ISBN: 3031437179
Category : Science
Languages : en
Pages : 215
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Book Description
This book starts with the mathematical basis of the theory - i.e. provide a brief sketch of the theory of manifolds and frame bundles, tensors and their transformations, relativistic kinematics, and aspects of non-flat space-time geometries. The definition of relevant physical quantities (torsion, curvature, non-metricity, tetrads, connection fields etc.) and important geometry concepts are also included. The main body of the book is devoted to a detailed derivation of the gauge theory of gravitation for scalar, vector (Proca and Maxwell) and Dirac spinor fields. Alternative approaches based on the Noether theorem and on the spinorial representation of the fields are also addressed, as well as important novel features related to the CCGG framework (Birkhoff theorem, field derivative identities etc.). In the last section of the volume the application of the CCGG theory to cosmology will be set out, resulting in a new understanding of dark energy and inflation.
Author: J.V. Narlikar
Publisher: Springer Science & Business Media
ISBN: 9400945086
Category : Science
Languages : en
Pages : 477
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Book Description
For several decades since its inception, Einstein's general theory of relativity stood somewhat aloof from the rest of physics. Paradoxically, the attributes which normally boost a physical theory - namely, its perfection as a theoreti cal framework and the extraordinary intellectual achievement underlying i- prevented the general theory from being assimilated in the mainstream of physics. It was as if theoreticians hesitated to tamper with something that is manifestly so beautiful. Happily, two developments in the 1970s have narrowed the gap. In 1974 Stephen Hawking arrived at the remarkable result that black holes radiate after all. And in the second half of the decade, particle physicists discovered that the only scenario for applying their grand unified theories was offered by the very early phase in the history of the Big Bang universe. In both cases, it was necessary to discuss the ideas of quantum field theory in the background of curved spacetime that is basic to general relativity. This is, however, only half the total story. If gravity is to be brought into the general fold of theoretical physics we have to know how to quantize it. To date this has proved a formidable task although most physicists would agree that, as in the case of grand unified theories, quantum gravity will have applications to cosmology, in the very early stages of the Big Bang universe. In fact, the present picture of the Big Bang universe necessarily forces us to think of quantum cosmology.
Author: Jasjeet Singh Bagla
Publisher: Springer
ISBN: 3319517007
Category : Science
Languages : en
Pages : 491
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Book Description
This book provides a compilation of in-depth articles and reviews on key topics within gravitation, cosmology and related issues. It is a celebratory volume dedicated to Prof. Thanu Padmanabhan ("Paddy"), the renowned relativist and cosmologist from IUCAA, India, on the occasion of his 60th birthday. The authors, many of them leaders of their fields, are all colleagues, collaborators and former students of Paddy, who have worked with him over a research career spanning more than four decades. Paddy is a scientist of diverse interests, who attaches great importance to teaching. With this in mind, the aim of this compilation is to provide an accessible pedagogic introduction to, and overview of, various important topics in cosmology, gravitation and astrophysics. As such it will be an invaluable resource for scientists, graduate students and also advanced undergraduates seeking to broaden their horizons.
Author: L. Sriramkumar
Publisher: World Scientific
ISBN: 9814322067
Category : Science
Languages : en
Pages : 284
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Book Description
This book comprises expository articles on different aspects of gravitation and cosmology that are aimed at graduate students. The topics discussed are of contemporary interest assuming only an elementary introduction to gravitation and cosmology. The presentations are to a certain extent pedagogical in nature, and the material developed is not usually found in sufficient detail in recent textbooks in these areas.
Author: Peter G. Bergmann
Publisher: Springer
ISBN:
Category : Science
Languages : en
Pages : 528
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Book Description
