Cosmology in Scalar-Tensor Gravity covers all aspects of cosmology in scalar-tensor theories of gravity. Considerable progress has been made in this exciting area of physics and this book is the first to provide a critical overview of the research. Among the topics treated are: -Scalar-tensor gravity and its limit to general relativity, -Effective energy-momentum tensors and conformal frames, -Gravitational waves in scalar-tensor cosmology, -Specific scalar-tensor theories, -Exact cosmological solutions and cosmological perturbations, -Scalar-tensor scenarios of the early universe and inflation, -Scalar-tensor models of quintessence in the present universe and their far-reaching consequences for the ultimate fate of the cosmos.

A pedagogical overview of the theoretical ideas behind the cosmological constant problem, in particular the scalar-tensor theory, which is one of the most popular alternative theories of gravitation. Covering many developments in the field, including branes and quintessence, it will be an invaluable resource for graduate students and researchers alike.

This book deals with the relationship between gravitation and elementary particle physics, and the implications of these subjects for astrophysics. There has, in recent years, been renewed interest in theories that connect up gravitation and particle physics, and in the astrophysical consequences of such theories. Some of these accounts involve a time-variation of the Newtonian gravitational parameter, G. In this respect, the present book may be regarded as a companion to my Cosmology and Geophysics (Hilger, Bristol, 1978). There is some overlap as regards the discussion of G-variability, but the emphasis in the present book is on astrophysics while the emphasis in the other one is on geophysics. The subject is a very broad one indeed, and in giving a review of it I have adopted a somewhat unorthodox way of presenting the material involved. The main reason for this is that a review of such a wide subject should aim at two levels: the level of the person who is interested in it, and the level of the person who is professionally engaged in research into it. To achieve such a two-level coverage, I have split the text up into two parts. The first part (Chapters 1-7) represents a relatively non-technical overview of the subject, while the second part (Chapters 8-11) represents a technical examination of the most important aspects of non-Einsteinian gravitational theory and its relation to astrophysics.

This book describes several basic results and applications of global aspects in gravitation theory and cosmology within the framework of Einstein's theory of gravity. Topics include results on the structure and topology of space-time, exact solutions to Einstein equations and singularities, the status of quantum gravity, and quantum effects near space-time singularities in strong curvature fields. Also covered are the global upper limits in cosmology on elementary particle masses which might constitute the dark matter of the universe. After discussing in detail the fundamental role played by global considerations in gravity and general relativity, the author points out the significant problems that remain: the nature and structure of space-time singularities, the cosmic censorship problem in black hole physics, and the issue of quantum effects in strong gravity fields. The author's treatment of gravitational collapse illustrates how powerfully-strong curvature naked singularities could result from the continual gravitational collapse of matter with several reasonable equations of state--including inflowing radiation, dust, or a perfect fluid. Students and mathematicians, astrophysicists, and physicists will find this theoretically rich book a landmark in relativity theory.

A comprehensive review of the testing and research conducted on Einstein's theory of general relativity.

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.

The 2015 centenary of the publication of Einstein's general theory of relativity, and the first detection of gravitational waves have focused renewed attention on the question of whether Einstein was right. This review of experimental gravity provides a detailed survey of the intensive testing of Einstein's theory of gravity, including tests in the emerging strong-field dynamical regime. It discusses the theoretical frameworks needed to analyze gravitational theories and interpret experiments. Completely revised and updated, this new edition features coverage of new alternative theories of gravity, a unified treatment of gravitational radiation, and the implications of the latest binary pulsar observations. It spans the earliest tests involving the Solar System to the latest tests using gravitational waves detected from merging black holes and neutron stars. It is a comprehensive reference for researchers and graduate students working in general relativity, cosmology, particle physics and astrophysics.

An up-to-date description of progress and current problems with the gravitational constant, both in terms of generalized gravitational theories and experiments either in the laboratory, using Casimir force measurements, or in space at solar system distances and in cosmological observations. Contributions cover different aspects of the state and prediction of unified theories of the physical interactions including gravitation as a cardinal link, the role of experimental gravitation and observational cosmology in discriminating between them, the problem of the precise measurement and stability of fundamental physical constants in space and time, and the gravitational constant in particular. Recent advances discussed include unified and scalar-tensor theories, theories in diverse dimensions and their observational windows, gravitational experiments in space, rotational and torsional effects in gravity, basic problems in cosmology, early universe as an arena for testing unified models, and big bang nucleosynthesis.

This thesis presents several significant new results that shed light on two major puzzles of modern cosmology: the nature of inflation, the very early phase of the universe that is thought to have given rise to the large-scale structures that we observe today; and that of the current accelerated expansion. In particular, it develops a clean method for characterizing linear cosmological perturbations for general theories where gravity is modified and/or affected by a new component, called dark energy, responsible for the accelerated expansion. It proposes a new extension to what were long thought to be the most general scalar field theories devoid of instabilities, and demonstrates the robustness of the relation between the energy scale of inflation and the predicted amplitude of gravitational waves. Finally, it consolidates a set of consistency relations between correlation functions of the cosmological density field and investigates the phenomenological consequences of their potential violation. Presented in a clear, succinct and rigorous style, each of these original results is both profound and important and will leave a deep mark on the field.