The Physics Of Time Reversal

The notion that fundamental equations governing the motions of physical systems are invariant under the time reversal transformation (T) has been an important, but often subliminal, element in the development of theoretical physics. It serves as a powerful and useful tool in analyzing the structure of matter at all scales, from gases and condensed matter to subnuclear physics and the quantum theory of fields. The assumption of invariance under T was called into question, however, by the 1964 discovery that a closely related assumption, that of CP invariance (where C is charge conjugation and P is space inversion), is violated in the decay of neutral K mesons. In The Physics of Time Reversal, Robert G. Sachs comprehensively treats the role of the transformation T, both as a tool for analyzing the structure of matter and as a field of fundamental research relating to CP violation. For this purpose he reformulates the definitions of T, P, and C so as to avoid subliminal assumptions of invariance. He summarizes the standard phenomenology of CP violation in the K-meson system and addresses the question of the mysterious origin of CP violation. Using simple examples based on the standard quark model, Sachs summarizes and illustrates how these phenomenological methods can be extended to analysis of future experiments on heavy mesons. He notes that his reformulated approach to conventional quantum field theory leads to new questions about the meaning of the transformations in the context of recent theoretical developments such as non-Abelian gauge theories, and he suggests ways in which these questions may lead to new directions of research.

This book introduces new developments in the field of Time-Reversal Symmetry presenting, for the first time, the Wigner time-reversal operator in the form of a product of two- or three time-reversal operators of lower symmetry. The action of these operators leads to the sign change of only one or two angular momentum components, not of all of them. It demonstrates that there are six modes of time-reversal symmetry breaking that do not lead to the complete disappearance of the symmetry but to its lowering. The full restoration of the time-reversal symmetry in the six cases mentioned is possible by introducing six types of metaparticles. The book also confirms the presence of six additional time-reversal operators using a group-theoretical method. The problem is only where to seek these metaparticles. The book discusses time-reversal symmetry in classical mechanics, classical and relativistic electrodynamics, quantum mechanics and theory of quantized fields, including dynamical reversibility and statistical irreversibility of the time, Wigner’s and Herring’s criteria, Kramers theorem, selection rules due to time-reversal symmetry, Onsager’s relations, Poincaré recurrence theorem, and CPT theorem. It particularly focuses attention on time-reversal symmetry violation. It is proposed a new method of testing the time-reversal symmetry, which is confirmed experimentally by EPR spectroscopy data. It shows that the traditional black-white point groups of magnetic symmetry are not applicable to magnetic systems with Kramers degeneration of energy levels and that magnetic groups of four-color symmetry are adequate for them. Further, it addresses the predicted structural distortions in Kramers three-homonuclear magnetic clusters due to time-reversal symmetry that have been identified experimentally. Lastly, it proposes a method of synthesis of two-nuclear coordination compounds with predictable magnetic properties, based on the application of the time-reversal transformation that was confirmed experimentally.

This book is the story of a physicist who will never see three score years and ten again, and who, during his long and chequered career, has lived through many events, met all kinds of people, known many distinguished scientists, and tried, not always successfully, to bring some original contributions to a field of physics born after the Second World War, nuclear magnetism.

The arrow of time refers to the curious asymmetry that distinguishes the future from the past. Reversing the Arrow of Time argues that there is an intimate link between the symmetries of 'time itself' and time reversal symmetry in physical theories, which has wide-ranging implications for both physics and its philosophy. This link helps to clarify how we can learn about the symmetries of our world; how to understand the relationship between symmetries and what is real, and how to overcome pervasive illusions about the direction of time. Roberts explains the significance of time reversal in a way that intertwines physics and philosophy, to establish what the arrow of time means and how we can come to know it. This book is both mathematically and philosophically rigorous yet remains accessible to advanced undergraduates in physics and philosophy of physics. This title is also available as Open Access on Cambridge Core.

The choice of topics in this book may seem somewhat arbitrary, even though we have attempted to organize them in a logical structure. The contents reflect the path of 'search and discovery' followed by us, on and off, for the in fact last twenty years. In the winter of 1970-71 one of the authors (C. A. ), on sah baticalleave with L. R. O. Storey's research team at the Groupe de Recherches Ionospheriques at Saint-Maur in France, had been finding almost exact symme tries in the computed reflection and transmission matrices for plane-stratified magnetoplasmas when symmetrically related directions of incidence were com pared. At the suggestion of the other author (K. S. , also on leave at the same institute), the complex conjugate wave fields, used to construct the eigenmode amplitudes via the mean Poynting flux densities, were replaced by the adjoint wave fields that would propagate in a medium with transposed constitutve tensors, et voila, a scattering theorem-'reciprocity in k-space'-was found in the computer output. To prove the result analytically one had to investigate the properties of the adjoint Maxwell system, and the two independent proofs that followed, in 1975 and 1979, proceeded respectively via the matrizant method and the thin-layer scattering-matrix method for solving the scattering problem, according to the personal preferences of each of the authors. The proof given in Chap. 2 of this book, based on the hindsight provided by our later results, is simpler and much more concise.

The asymmetry of natural phenomena under time reversal is striking. Here Zehinvestigates the most important classes of physical phenomena that characterize the arrow of time, discussing their interrelations as well as striving to uncover a cosmological common root of the phenomena, such as the time-independent wave function of the universe. The description of irreversible phenomena is shown to be fundamentally "observer-related". Both physicists and philosophers of science who reviewed the first edition considered this book a magnificent survey, a concise, technically sophisticated, up-to-date discussion of the subject, showing fine sensivity to some of the crucial philosophicalsubtleties. This new and expanded edition will be welcomed by both students and specialists.

This book presents the classical theorems about simply connected smooth 4-manifolds: intersection forms and homotopy type, oriented and spin bordism, the index theorem, Wall's diffeomorphisms and h-cobordism, and Rohlin's theorem. Most of the proofs are new or are returbishings of post proofs; all are geometric and make us of handlebody theory. There is a new proof of Rohlin's theorem using spin structures. There is an introduction to Casson handles and Freedman's work including a chapter of unpublished proofs on exotic R4's. The reader needs an understanding of smooth manifolds and characteristic classes in low dimensions. The book should be useful to beginning researchers in 4-manifolds.