The search for a theory of quantum gravity is one of the most important and fascinating problems in modern theoretical physics. While we do not have yet a complete theory of quantum gravity, significant advancements have been done in the past decades. In this handbook, every section is dedicated to a specific approach towards a theory of quantum gravity and is edited by the leading experts in the field. This book represents both a valuable resource for graduate students and an important reference for researchers in quantum gravity.

This book is aimed at theoretical and mathematical physicists and mathematicians interested in modern gravitational physics. I have thus tried to use language familiar to readers working on classical and quantum gravity, paying attention both to difficult calculations and to existence theorems, and discussing in detail the current literature. The first aim of the book is to describe recent work on the problem of boundary conditions in one-loop quantum cosmology. The motivation of this research was to under­ stand whether supersymmetric theories are one-loop finite in the presence of boundaries, with application to the boundary-value problemsoccurring in quantum cosmology. Indeed, higher-loop calculations in the absence of boundaries are already available in the litera­ ture, showing that supergravity is not finite. I believe, however, that one-loop calculations in the presence of boundaries are more fundamental, in that they provide a more direct check of the inconsistency of supersymmetric quantum cosmology from the perturbative point of view. It therefore appears that higher-order calculations are not strictly needed, if the one-loop test already yields negative results. Even though the question is not yet settled, this research has led to many interesting, new applications of areas of theoretical and mathematical physics such as twistor theory in flat space, self-adjointness theory, the generalized Riemann zeta-function, and the theory of boundary counterterms in super­ gravity. I have also compared in detail my work with results by other authors, explaining, whenever possible, the origin of different results, the limits of my work and the unsolved problems.

This handbook provides an updated comprehensive description of gravitational wave astronomy. In the first part, it reviews gravitational wave experiments, from ground and space based laser interferometers to pulsar timing arrays and indirect detection from the cosmic microwave background.

This second edition offers a comprehensive introduction to loop quantum gravity (LQG) in self-dual variables, including the necessary prerequisites. Additionally, it delves into various significant research areas that have emerged in recent years. New content (including an entirely new chapter dedicated to dynamics of quantum spacetime) explores the description of spin networks and spin-foams, their historical development as well as connections to tensor networks, BF theory, and emerging approaches including the spinorial representation of LQG, SU(2) coherent states, and group field theory. Furthermore, the book provides expanded appendices covering essential tools and concepts, such as the connection between information theory and entropy, and overviews of group theory and differential geometry. All topics are presented from a non-expert perspective, ensuring self-containment and accessibility. The primary aim of this second edition remains helping researchers, bewildered by the vast array of topics within this rapidly growing field of quantum gravity, to gain a fundamental understanding of the current developments.

This Brief presents a new way of introducing relativity theory, in which perplexing relativistic effects such as time dilation and Lorentz contraction are explained prior to the discussion of Lorentz-transformation. The notion of relativistic mass is shown to contradict the spirit of relativity theory and the true significance of the mass-energy relation is contrasted with the popular view of it. The author discusses the twin paradox from the point of view of both siblings. Last but not least, the fundamentals of general relativity are described, including the recent Gravity Probe B experiment.

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.

The majority of books dealing with prospects for interstellar flight tackle the problem of the propulsion systems that will be needed to send a craft on an interstellar trajectory. The proposed book looks at two other, equally important aspects of such space missions, and each forms half of this two part book.

The main feature of this book is the emphasis on "practice". This approach, unusual in the relativistic literature, may be clarified by quoting some problems discussed in the text: - the analysis of rocket acceleration to relativistic velocities - the influence of gravitational fields on the accuracy of time measurements - the operation of optical rotation sensors - the evaluation of the Doppler spectrum produced by the linear (or ro- tional) motion of an antenna or scatterer - the use of the Cerenkov effect in the design of millimeter-wave power generators - the influence of the motion of a plasma on the transmission of electrom- netic waves through this medium. A correct solution of these (and analogous) problems requires the use of re­ lativistic principles.

Understanding the stars is the bedrock of modern astrophysics. Stars are the source of life. The chemical enrichment of our Milky Way and of the Universe withallelementsheavierthanlithiumoriginatesintheinteriorsofstars.Stars arethe tracersofthe dynamics ofthe Universe,gravitationallyimplying much more than meets the eye. Stars ionize the interstellar medium and re-ionized the early intergalactic medium.

This reference textbook is an up-to-date and self-contained introduction to the theory of gravitational interactions. The first part of the book follows the traditional presentation of general relativity as a geometric theory of the macroscopic gravitational field. A second, advanced part then discusses the deep analogies (and differences) between a geometric theory of gravity and the gauge theories of the other fundamental interactions. This fills a gap which is present in the context of the traditional approach to general relativity, and which usually makes students puzzled about the role of gravity. The necessary notions of differential geometry are reduced to the minimum, leaving more room for those aspects of gravitational physics of current phenomenological and theoretical interest, such as the properties of gravitational waves, the gravitational interactions of spinors, and the supersymmetric generalization of the Einstein equations.

This expanded second edition of Relativity and the Nature of Spacetime c- tains several major changes and a number of additions to different ch- ters. Two chapters (Chaps. 6 and 7), which discussed two speci?c groups of arguments against the reality of spacetime, have been transformed into - pendices (A and B). Two new chapters (Chaps. 6 and 10) have been added. Chapter 6, entitled Why Is the Issue of the Nature of Spacetime So Imp- tant?, elaborates on what was Sect. 5. 6 of the ?rst edition, and addresses some recent work on the nature of spacetime – for example, the growing (or evolving) block universe model of the world, which has recently been - vived by several physicists as what appears to be the last remaining alter- tive to the Minkowski absolute four-dimensional world (after it had become an undeniable fact that three-dimensionalism, or presentism, contradicts the relativistic experimental evidence). Chapter 10, entitled Spacetime and the Nature of Quantum Objects and based on what used to be Sects. 6. 2 and 6. 3 in the ?rst edition, explores the implications of the issue of the nature of spacetime for quantum physics, in order to see whether it can provide some insight into the nature of quantum objects. Two new sections have been included, namely, Sect. 5. 6 entitled Re- tivization of Existence and Observers in General Relativity and Sect. 7. 6 - titled Probing the Anisotropic Velocity of Light by a Terrestrial Experiment.

Für die Studierenden der Physik im Haupt- und Nebenfach ist der Gerthsen ein unverzichtbarer und kompetenter Begleiter durch das gesamte Studium. Nahezu alle Studierenden beginnen mit dem Klassiker Gerthsen. Sämtliche Gebiete der Physik werden ausführlich und gut verständlich dargestellt. Das Buch stellt alle klassischen Themen vor - Mechanik, Wärmelehre, Elektrodynamik, Optik. Darauf aufbauende Themen der klassischen Physik wie die Nichtlineare Dynamik und die Relativitätstheorie sind in logischer Reihenfolge integriert. Nach einem Kapitel über Teilchen und Wellen zur Einführung in die mikroskopische Physik werden die Konsequenzen für Atome, Moleküle, Laser, feste Körper und subatomare Teilchen vorgestellt.