Gravitation

. The main aim of this book is to shine a spotlight on key experiments and their crucial importance for advancing our understanding of physics. Physics is an empirical science, and experiments have always been a driving force in the development of our understanding of nature. Facts matter. In that sense, the book attempts to be complementary to the many popularizations of theoretical physics, and to counterbalance the frequent emphasis there on more speculative ideas.Experimental physics is also an essential pillar in physics teaching, as well as helping broader audiences to better understand important concepts, particularly in challenging fields such as relativity or quantum physics, where our common sense intuition often fails.Readers are taken on an historical journey, starting with ¿Free Fall¿ and culminating in ¿Spooky Action at a Distance¿. En route they will encounter many important branches ofphysics, whose main ideas and theoretical description will be given a more empirical meaning. At the end, the reader is invited to reflect on what could be exciting and important directions for fundamental physics. All readers with an undergraduate degree in physical sciences or engineering will enjoy and learn much from this stimulating and original text.

This book provides a mathematical and numerical analysis of many problems which lead to paradoxes in contemporary cosmology, in particular, the existence of dark matter and dark energy. It is shown that these hypothetical quantities arise from excessive extrapolations of simple mathematical models to the whole physical universe. Written in a completely different style to most books on General Relativity and cosmology, the important results take the form of mathematical theorems with precise assumptions and statements. All theorems are followed by a corresponding proof, or an exact reference to the proof.Some nonstandard topics are also covered, including violation of the causality principle in Newtonian mechanics, a critical mathematical and numerical analysis of Mercury's perihelion shift, inapplicability of Einstein's equations to the classical two-body problem due to computational complexity, non-uniqueness of the notion of universe, the topology of the universe, various descriptions of a hypersphere, regular tessellations of hyperbolic spaces, local Hubble expansion of the universe, neglected gravitational redshift in the detection of gravitational waves, and the possible distribution of mass inside a black hole. The book also dispels some myths appearing in the theory of relativity and in contemporary cosmology. For example, although the hidden assumption that Einstein's equations provide a good description of the evolution of the whole universe is considered to be obvious, it is just a null hypothesis which has not been verified by any experiment, and has only been postulated by excessive extrapolations of many orders of magnitude.

This book treats the subject of gravitational waves (GWs) production in binary stars or black-holes and in the early universe, using tools of quantum field theory which are familiar to graduate students and researchers in particle physics. A special focus is given to the generation of templates of gravitational wave signals from Feynman diagram calculations of transition amplitudes, which interests active researchers in GWs. The book presents field theory concepts, like supersymmetry realized in spinning binaries and soft-graviton theorems, that can have practical applications in novel GW signals, like the memory effect. The book also aims at specialists in both GWs and particle physics addressing cosmological models of phase transition and inflation that can be tested in observations at terrestrial and space based interferometers, pulsar timing arrays, and the cosmic microwave anisotropy observations.

This book provides a concise introduction to the physics of gravitational waves. It is aimed at graduate-level students and PhD scholars. Ever since the discovery of gravitational waves in 2016, gravitational wave astronomy has been adding to our understanding of the universe.Gravitational waves have been detected in the past few years from several transient events such as merging stellar-mass black holes, binary neutron stars, etc. These waves have frequencies in a band ranging from a few hundred hertz to around a kilohertz to which LIGO type instruments are sensitive. LISA will be sensitive to much lower range of frequencies from SMBH mergers. Apart from these cataclysmic burst events, there are innumerable sources of radiation which are continuously emitting gravitational waves of all frequencies. These include a whole mass range of compact binary and isolated compact objects and close planetary stellar entities. This book discusses the gravitational wave backgroundproduced in typical frequency ranges from such sources emitting over a Hubble time and the fluctuations in the h values measured in the usual devices. Also discussed are the high-frequency thermal background gravitational radiation from hot stellar interiors and newly formed compact objects. The reader will also learn how gravitational waves provide a testing tool for various theories of gravity, i.e. general relativity and extended theories of gravity, and will be the definitive test for general relativity.

The thesis tackles two distinct problems of great interest in gravitational mechanics ¿ one relativistic and one Newtonian. The relativistic one is concerned with the "first law of binary mechanics", a remarkably simple variational relation that plays a crucial role in the modern understanding of the gravitational two-body problem, thereby contributing to the effort to detect gravitational-wave signals from binary systems of black holes and neutron stars. The work reported in the thesis provides a mathematically elegant extension of previous results to compact objects that carry spin angular momentum and quadrupolar deformations, which more accurately represent astrophysical bodies than mere point particles. The Newtonian problem is concerned with the isochrone problem of celestial mechanics, namely the determination of the set of radial potentials whose bounded orbits have a radial period independent of the angular momentum. The thesis solves this problem completely ina geometrical way and explores its consequence on a variety of levels, in particular with a complete characterisation of isochrone orbits. The thesis is exceptional in the breadth of its scope and achievements. It is clearly and eloquently written, makes excellent use of images, provides careful explanations of the concepts and calculations, and it conveys the author¿s personality in a way that is rare in scientific writing, while never sacrificing academic rigor.

The framework of Quantum Field Theory (QFT) encompasses the mathematical structure of a wide variety of physical systems, including systems of particle physics, general relativity,statistical physics, and the early universe. QFT unifies Einstein's theory of relativity with quantummechanics, permitting us to describe the physics of the very small and the very fast in one unifiedframework. In QFT the fundamental object is a field that is valued at every point in spacetime, andparticles are excitations of these fundamental fields. One reason we must switch to thinking aboutfields rather than particles is that in relativistic processes, particles can be created or destroyed.When particle number is not conserved, we need a theory that can describe more than singleparticle dynamics. Another fundamental reason for a quantum theory of fields is that we need toconstruct laws of nature that are local, which requires taking into account the fact that informationtravels at a finite speed. QFT provides a natural framework for doing this

This textbook introduces special relativity with a focus on a profound understanding of the physics behind the theory. The main part of the book is targeted to undergraduates, for physics education, for undergraduate students in natural sciences in general, and even to interested laypersons. To serve these target groups, the book uses only basic mathematics and, in contrast to many other introductions to special relativity, the book is based on a pedagogical approach that relies on geometry and space-time diagrams to make the surprising predictions of the theory particularly clear. Special relativity is a geometric theory, and space-time diagrams are an efficient and easily understandable way to comprehend its implications.The textbook, however, is also suitable for advanced students and enthusiasts that already learned the basics of the special theory of relativity and want to know more. Special digression sections provide plenty of interesting material. Carefully selected problems with solutions and in-depth explanations for all key experiments help deepen the knowledge.

This book presents experimental work conducted on the International Space Station (ISS) in order to characterize metals and alloys in the liquid state. The internationally recognized authors present and discuss experiments performed in microgravity that enabled the study of the relevant volume and surface related properties free of the restrictions of a gravity-based environment. The collection serves also as a handbook of space experiments using electromagnetic levitation techniques. A summary of recent results provides an overview of the wealth of space experiment data, which will ignite further research activities and inspire academics and industrial research departments for their continuous development. 

"This Element critically investigates proposed tabletop experiments controversially claimed to produce and 'witness' the first laboratory quantum gravity phenomena"--

This self-contained monograph provides a mathematically simple and physically meaningful model which unifies gravity, electromagnetism, optics and even some quantum behavior. The simplicity of the model is achieved by working in the frame of an inertial observer and by using a physically meaningful least action principle.The authors introduce an extension of the Principle of Inertia. This gives rise to a simple, physically meaningful action function. Visualizations of the geometryare obtained by plotting the action function. These visualizations may be used to compare the geometries of different types of fields. Moreover, a new understanding of the energy-momentum of a field emerges.The relativistic dynamics derived here properly describes motion of massive and massless objects under the influence of a gravitational and/or an electromagnetic field, and under the influence of isotropic media.The reader will learn how to compute theprecession of Mercury, the deflection of light, and the Shapiro time delay. Also covered is the relativistic motion of binary stars, including the generation of gravitational waves, a derivation of Snell's Law and a relativistic description of spin. We derive a complex-valued prepotential of an electromagnetic field. The prepotential is similar to the wave function in quantum mechanics. The mathematics is accessible to students after standard courses in multivariable calculus and linear algebra. For those unfamiliar with tensors and the calculus of variations, these topics are developed rigorously in the opening chapters. The unifying model presented here should prove useful to upper undergraduate and graduate students, as well as to seasoned researchers.

The title and sub-title say a lot about what the concept of the book revolves around. What I can add here about it is that I originally posed this theory of gravity to be more of an alternate to general relativity (GR). After finishing the book and starting a paper to submit to a journal more became apparent to me. The concept in this book I first considered parallel to GR I now look at as a redefining of it instead. It won't redefine the entirety of it only the basis of the characteristic of gravitation. I've always believed the idea of curved space-time creating gravity to be an abstract mechanism. It does not go any further than that to explain the exact mechanism of why that creates gravity. It ends at that point which is why it seems abstract and that is an indication there is more to the process between curved space-time and gravitation. This book lays out that missing process with a detailed mechanism that shows a concrete real life process of physics that explains the way gravity functions. It also redefines the process of time dilation by extrapolating the genesis of it centering on an aspect of quantizing space-time. The entire process of gravity begins and ends with space-time. The end result of the process leading to gravitation is the manifestation of energy potential. It manifests in the fundamental fields of atoms which are normally balanced but while occupying relative space-time (curved space-time) become unbalanced. That imbalance is what creates energy potential with that converting to kinetic energy as motion. With a process that is inducing motion or gravitation in this way as energy potential it can only be seen as propulsive. From the beginning gravity has always been described as an attraction but with this new way of looking at it we can no longer follow that assumption. What is induced in objects of mass is propulsive and we can now use that as the characterization of gravity. Because this uses known fundamental forces for the action of gravity we can no longer look at gravity as a separate fundamental force. It acts as a characteristic therefore it is not one by itself. Because of this it presents a sort of unification of gravity with electromagnetism and the strong fundamental forces.Isaac Newton left the mechanism of gravity up to the reader to conceive and this concept is that. This can be considered that final step where he left off and a completion of his work. Albert Einstein created the basis of that step with the conception of time dilation and genesis of relative space-time for without it this concept would have no foundation. General relativity though is incomplete which is identified by ending at curved space-time as the end means for gravity. The concept in this book can be considered a redefining of the process proposed by GR. A completion creating a sort of GR 2.0 with no disrespect intended, Einstein just didn't realize GR was incomplete. If he had he may have had different results on his 30 year quest to unite GR and electromagnetism. Which may have also united classical and quantum mechanics by eliminating the search and need for quantum gravity.

This book consists of contributions from the participants of the Abel Symposium 2019 held in Ålesund, Norway. It was centered about applications of the ideas of symmetry and invariance, including equivalence and deformation theory of geometric structures, classification of differential invariants and invariant differential operators, integrability analysis of equations of mathematical physics, progress in parabolic geometry and mathematical aspects of general relativity.The chapters are written by leading international researchers, and consist of both survey and research articles. The book gives the reader an insight into the current research in differential geometry and Lie theory, as well as applications of these topics, in particular to general relativity and string theory.

This book, the first in a three-volume set, explains general relativity using the mathematical tool of differential geometry. The book consists of ten chapters, the first five of which introduce differential geometry, which is widely applicable even outside the field of relativity. Chapter 6 analyzes special relativity using geometric language. In turn, the last four chapters introduce readers to the fundamentals of general relativity. Intended for beginners, this volume includes numerous exercises and worked-out example in each chapter to facilitate the learning experience. Chiefly written for graduate-level courses, the book¿s content will also benefit upper-level undergraduate students, and can be used as a reference guide for practicing theoretical physicists.

This book presents a review of various issues related to Lorentz symmetry breaking. Explicitly, we consider (i) motivations for introducing Lorentz symmetry breaking, (ii) classical aspects of Lorentz-breaking field theory models including typical forms of Lorentz-breaking additive terms, wave propagation in Lorentz-breaking theories, and mechanisms for breaking the Lorentz symmetry; (iii) quantum corrections in Lorentz-breaking theories, especially the possibilities for perturbation generating the most interesting Lorentz-breaking terms; (iv) correspondence between non-commutative field theories and Lorentz symmetry breaking; (v) supersymmetric Lorentz-breaking theories; and (vi) Lorentz symmetry breaking in a curved space-time. We close the book with the review of experimental studies of Lorentz symmetry breaking.The importance and relevance of these topics are explained, first, by studies of limits of applicability of the Lorentz symmetry, second, by searches of the possible extensions of the standard model, including the Lorentz-breaking ones, and need to study their properties, third, by the relation between Lorentz symmetry breaking with string theory, fourth, by the problem of formulating a consistent quantum gravity theory, so that various modified gravity models are to be examined.

The book is about exact space-time models of the gravitational fields produced by gravitational radiation. The authors' extensive work in the field is reviewed in order to stimulate the study of such models, that have been known for a long time, and to highlight interesting physical aspects of the existing models in some novel detail. There is an underlying simplicity to the gravitational radiation studied in this book. Apart from the basic assumption that the radiation has clearly identifiable wave fronts, the gravitational waves studied are directly analogous to electromagnetic waves. The book is meant for advanced students and researchers who have a knowledge of general relativity sufficient to carry out research in the field.

This book is a small but practical summary of how one can and should learn science. The author argues that science cannot be taught but has to be learnt. Based on historical examples he shows that practicing science means putting one's intellect into the understanding of simple questions like what, why, how and when events around you happen. The reader understands that the search for the cause and effect relationship of so called normal happenings is a very provocative experience and learning science leads one to it. This is underpinned by looking at everyday experiences and how they can help any lay-person learn science.The author also explains the methodology of science and discusses an integrated approach to science communication. Finally he elaborates on the influence and role of science in society. The book addresses interested general readers, teachers and science communicators.

This proceedings volume gathers selected, revised papers presented at the X International Meeting on Lorentzian Geometry (GeLoCor 2021), virtually held at the University of Cordoba, Spain, on February 1-5, 2021. It includes surveys describing the state-of-the-art in specific areas, and a selection of the most relevant results presented at the conference. Taken together, the papers offer an invaluable introduction to key topics discussed at the conference and an overview of the main techniques in use today.This volume also gathers extended revisions of key studies in this field. Bringing new results and examples, these unique contributions offer new perspectives to the original problems and, in most cases, extend and reinforce the robustness of previous findings.Hosted every two years since 2001, the International Meeting on Lorentzian Geometry has become one of the main events bringing together the leading experts on Lorentzian geometry. In this volume, the reader will find studies on spatial and null hypersurfaces, low regularity in general relativity, conformal structures, Lorentz-Finsler spacetimes, and more.Given its scope, the book will be of interest to both young and experienced mathematicians and physicists whose research involves general relativity and semi-Riemannian geometry. 

The purpose of this book is to illustrate some of the most important techniques which are helpful in combinatorial problems when computing quantum effects in covariant theories, like general relativity. In fact, most of the techniques find application also in broader contexts, such as low energy effective (chiral) Lagrangians or even in specific problems in condensed matter. Some of the topics covered are: the background field approach and the heat kernel ideas. The arguments are explained in some detail and the presentation is meant for young researchers and advanced students who are starting working in the field. As prerequisite the reader should have attended a course in quantum field theory including Feynman's path integral. In the Appendix a nontrivial calculation of one-loop divergences in Einstein-Hilbert gravity is explained step-by-step.