Claus Kiefer – författare

The description of Nature in physics currently falls into two parts: the microscopic and the macroscopic. The microscopic world (molecules, atoms, particles) is described by quantum theory, whereas the macroscopic world (planets, stars, galaxies, universe) is ruled by a classical interaction - gravity - that is described by Einstein's theory of general relativity. This book describes in detail the attempts to unify quantum theory and relativity, which are essential to understanding the origin of the Universe and the final fate of black holes. The construction of a consistent quantum theory is among the most important open problems in fundamental physics. This book describes the motivation for constructing such a theory and presents the main approaches. These approaches include covariant quantization, canonical quantization (metric and loop approaches), and string theory. The book also covers the main applications, which include black holes and cosmology. This new edition includes updated content throughout, as well as further explorations of the holographic principle, unimodular gravity, quantum-gravitational correction terms, and possible observations, as these are topics that have experienced important developments since the last edition.

The search for a quantum theory of the gravitational field is one of the great open problems in theoretical physics. This book presents a self-contained discussion of the concepts, methods and applications that can be expected in such a theory. The two main approaches to its construction -- the direct quantisation of Einstein's general theory of relativity and string theory -- are covered. Whereas the first attempts to construct a viable theory for the gravitational field alone, string theory assumes that a quantum theory of gravity will be achieved only through a unification of all the interactions. However, both employ the general method of quantization of constrained systems, which is described together with illustrative examples relevant for quantum gravity. There is a detailed presentation of the main approaches employed in quantum general relativity: path-integral quantization, the background-field method and canonical quantum gravity in the metric, connection and loop formulations. The discussion of string theory centres around its quantum-gravitational aspects and the comparison with quantum general relativity. Physical applications discussed at length include the quantization of black holes, quantum cosmology, the indications of a discrete structure of spacetime, and the origin of irreversibility.This third edition contains new chapters or sections on quantum gravity phenomenology, Horava-Lifshitz quantum gravity, analogue gravity, the holographic principle, and affine quantum gravity. It will present updates on loop quantum cosmology, the LTB model, asymptotic safety, and various discrete approaches. The third edition also contains pedagogical extensions throughout the text.This book will be of interest to researchers and students working in relativity and gravitation, cosmology, quantum field theory and related topics. It will also be of interest to mathematicians and philosophers of science.

The entanglement of quantum mechanics plays a central role in experiments with atoms and photons (Nobel Prize 2012 for Haroche and Wineland) and the planned construction of quantum computers.

The entanglement of quantum mechanics plays a central role in experiments with atoms and photons (Nobel Prize 2012 for Haroche and Wineland) and the planned construction of quantum computers.

This book presents a multidisciplinary guide to gauge theory and gravity, with chapters by the world’s leading theoretical physicists, mathematicians, historians and philosophers of science. The contributions from theoretical physics explore e.g. the consistency of the unification of gravitation and quantum theory, the underpinnings of experimental tests of gauge theory and its role in shedding light on the relationship between mathematics and physics. In turn, historians and philosophers of science assess the impact of Weyl’s view on the philosophy of science.   Graduate students, lecturers and researchers in the fields of history of science, theoretical physics and philosophy of science will benefit from this book by learning about the role played by Weyl’s Raum-Zeit-Materie in shaping several modern research fields, and by gaining insights into the future prospects of gauge theory in both theoretical and experimental physics. Furthermore, the book facilitates interdisciplinary exchange and conceptual innovation in tackling fundamental questions about our deepest theories of physics. Chapter “Weyl’s Raum-Zeit-Materie and the Philosophy of Science” is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com

This book presents a multidisciplinary guide to gauge theory and gravity, with chapters by the world’s leading theoretical physicists, mathematicians, historians and philosophers of science. The contributions from theoretical physics explore e.g. the consistency of the unification of gravitation and quantum theory, the underpinnings of experimental tests of gauge theory and its role in shedding light on the relationship between mathematics and physics. In turn, historians and philosophers of science assess the impact of Weyl’s view on the philosophy of science.   Graduate students, lecturers and researchers in the fields of history of science, theoretical physics and philosophy of science will benefit from this book by learning about the role played by Weyl’s Raum-Zeit-Materie in shaping several modern research fields, and by gaining insights into the future prospects of gauge theory in both theoretical and experimental physics. Furthermore, the book facilitates interdisciplinary exchange and conceptual innovation in tackling fundamental questions about our deepest theories of physics. Chapter “Weyl’s Raum-Zeit-Materie and the Philosophy of Science” is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com

Quantum theory is at the foundation of the physical description of our world. This volume provides illuminating reading to anyone seeking a deep understanding of quantum theory and its relevance to the foundations of physics.

Quantum theory is at the foundation of the physical description of our world. This volume provides illuminating reading to anyone seeking a deep understanding of quantum theory and its relevance to the foundations of physics.

When we were preparing the first edition of this book, the concept of de­ coherence was known only to a minority of physicists. In the meantime, a wealth of contributions has appeared in the literature - important ones as well as serious misunderstandings. The phenomenon itself is now experimen­ tally clearly established and theoretically well understood in principle. New fields of application, discussed in the revised book, are chaos theory, informa­ tion theory, quantum computers, neuroscience, primordial cosmology, some aspects of black holes and strings, and others. While the first edition arose from regular discussions between the authors, thus leading to a clear" entanglement" of their otherwise quite different chap­ ters, the latter have thereafter evolved more or less independently. While this may broaden the book's scope as far as applications and methods are con­ cerned, it may also appear confusing to the reader wherever basic assumptions and intentions differ (as they do). For this reason we have rearranged the or­ der of the authors: they now appear in the same order as the chapters, such that those most closely related to the "early" and most ambitious concept of decoherence are listed first. The first three authors (Joos, Zeh, Kiefer) agree with one another that decoherence (in contradistinction to the Copen­ hagen interpretation) allows one to eliminate primary classical concepts, thus neither relying on an axiomatic concept of observables nor on a probability interpretation of the wave function in terms of classical concepts.

The relation between quantum theory and the theory of gravitation remains one of the most outstanding unresolved issues of modern physics. According to general expectation, general relativity as well as quantum (field) theory in a fixed background spacetime cannot be fundamentally correct. Hence there should exist a broader theory comprising both in appropriate limits, i. e. , quantum gravity. This book gives readers a comprehensive introduction accessible to interested non-experts to the main issues surrounding the search for quantum gravity. These issues relate to fundamental questions concerning the various formalisms of quantization; specific questions concerning concrete processes, like gravitational collapse or black-hole evaporation; and the all important question concerning the possibility of experimental tests of quantum-gravity effects.

This book addresses graduate students in the first place and is meant as a modern compendium to the existing texts on black hole astrophysics. The authors present in pedagogically written articles our present knowledge on black holes covering mathematical models including numerical aspects and physics and astronomical observations as well. In addition, in their write-up of a panel discussion the participants of the school address the existence of black holes consenting that it has by now been verified with certainty.

When we were preparing the first edition of this book, the concept of de­ coherence was known only to a minority of physicists. In the meantime, a wealth of contributions has appeared in the literature - important ones as well as serious misunderstandings. The phenomenon itself is now experimen­ tally clearly established and theoretically well understood in principle. New fields of application, discussed in the revised book, are chaos theory, informa­ tion theory, quantum computers, neuroscience, primordial cosmology, some aspects of black holes and strings, and others. While the first edition arose from regular discussions between the authors, thus leading to a clear" entanglement" of their otherwise quite different chap­ ters, the latter have thereafter evolved more or less independently. While this may broaden the book's scope as far as applications and methods are con­ cerned, it may also appear confusing to the reader wherever basic assumptions and intentions differ (as they do). For this reason we have rearranged the or­ der of the authors: they now appear in the same order as the chapters, such that those most closely related to the "early" and most ambitious concept of decoherence are listed first. The first three authors (Joos, Zeh, Kiefer) agree with one another that decoherence (in contradistinction to the Copen­ hagen interpretation) allows one to eliminate primary classical concepts, thus neither relying on an axiomatic concept of observables nor on a probability interpretation of the wave function in terms of classical concepts.

The relation between quantum theory and the theory of gravitation remains one of the most outstanding unresolved issues of modern physics. According to general expectation, general relativity as well as quantum (field) theory in a fixed background spacetime cannot be fundamentally correct.

Originaltext und ausführlicher historischer Kommentar von Claus KieferDie Arbeit von Einstein, Podolsky und Rosen (EPR) aus dem Jahr 1935 gehört zu den Klassikern der modernen Physik. In ihr wird zum ersten Mal die zentrale Eigenschaft der Quantentheorie thematisiert: die Verschränkung. Im allgemeinen sind Systeme in der Natur miteinander verschränkt, das heißt, sie besitzen nur einen gemeinsamen, nicht aufteilbaren, Zustand. Diese Tatsache ist für alle Merkwürdigkeiten verantwortlich, die gemeinhin mit der Quantentheorie in Verbindung gebracht werden, wozu die Gedankenexperimente mit Schrödingers Katze und Wigners Freund zählen. Die Verschränkung quantenmechanischer Systeme spielt eine zentrale Rolle bei Experimenten mit Atomen und Photonen (Nobelpreis 2012 für Haroche und Wineland) und der geplanten Konstruktion von Quantencomputern. Das Buch bringt die Originalarbeit von EPR in deutscher Übersetzung und einen ausführlichen Kommentarteil, der sowohl den historischen Kontextder Arbeit beleuchtet als auch auf alle Aspekte der Verschränkung eingeht. Es widmet sich insbesondere der Interpretation der Quantentheorie und deren Konsequenzen für ein grundlegendes Verständnis der Natur.

Die angesehenen Wissenschaftler Domenico Giulini und Claus Kiefer geben in diesem essential einen kompakten Überblick über dieses Phänomen der theoretischen Physik und über die indirekten und die kürzlich gelungenen direkten Nachweise von Gravitationswellen.