Particle Astrophysics Second Edition

Author: D. H. PERKINS

Published in: Oxford University Press

ISBN: 978–0–19–954546–9

File Type: pdf

File Size:  4 MB

Language: English


Particle Astrophysics is an enlarged and updated version of the first edition published in 2003. In a rapidly evolving field, emphasis has of course been placed on the most recent developments. However, I have also taken the opportunity to re-arrange the material and present it in more detail and at somewhat greater length. For convenience, the text has been divided into three parts. Part 1, containing Chapters 1–4, deals basically with the fundamental particles and their interactions, as observed in laboratory experiments, which are covered by the so-called Standard Model of particle physics. This model gives an extremely exact and detailed account of an immense mass of experimental data obtained at accelerators worldwide, although some postulated phenomena such as the Higgs boson have still to be observed.

Developments beyond the original Standard Model, particularly the subject of neutrino masses and flavour oscillations, are included, as well as possible extensions of the model, such as supersymmetry and the grand unification of the fundamental interactions. I have also taken the opportunity to present in Chapter 2, a short account of relativistic transformations, the equivalence principle and solutions of the field equations of general relativity which are important for astrophysics. Part 2 (Chapters 5–8) describes the present picture of the cosmos in the large, with emphasis on the basic parameters of the early universe, which are now becoming more accurately known and expressed in the so-called Concordance Model of cosmology.

This part also underlines the great questions and mysteries in cosmology: the nature of dark matter; the nature of dark energy and the magnitude of the cosmological constant; the matter–antimatter asymmetry of the universe; the precise mechanism of inflation; and, just as is the case for the 20 or so parameters describing the Standard Model of particles, the arbitrary nature of the parameters in the Concordance Model. Part 3 (Chapters 9 and 10) is concerned with the study of the particles and radiation which bombard us from outer space, and to the stellar phenomena, such as pulsars, active galactic nuclei, black holes, and supernovae which appear to be responsible for this ‘cosmic rain’. We encounter here some of the most energetic and bizarre processes in the universe, with new experimental discoveries being made on an almost daily basis. By and large, the above division of the subject matter in a sense also reflects the state of our knowledge in the three cases. One could say that particle physics at accelerators in Part 1 is an extremely well-understood subject, with agreement between theory and experiment better than one part per million in the case of quantum electrodynamics.

Whatever the form might be of an ultimate ‘theory of everything’—-if there ever is one—-the Standard Model of particle physics will surely be part of it, even if it only accounts for a paltry 4% of the energy density of the universe at large. Our knowledge of the basic parameters of cosmology in Part 2, while less exact is now, as compared with just a decade ago, reaching quite remarkable levels of precision, as described in the Concordance Model. In contrast, the wide-ranging study of the particles and radiation in Part 3 leaves very many open questions and is probably the least well-understood aspect of particle astrophysics. For example, a century after they were first discovered, it is only recently that we have gained some idea on how the cosmic rays are accelerated to the very highest energies (of the order of 1020 eV) that can be detected and, more than 30 years after their first detection, we still do not know what is the underlying mechanism of γ-ray bursts, perhaps the most violent events taking place in the present universe. Some subjects appropriate to particle astrophysics have been left out, either through lack of space or because I thought they might be too advanced or too speculative. As in the first edition, the general theory of relativity has been omitted, although in Chapter 2, I have tried to give some plausibility arguments, based on the equivalence principle and special relativity, to illustrate important solutions of the Einstein field equations.

General relativity is in any case adequately covered by the companion volume on Gravitation, Relativity and Cosmology by T.P. Cheng in the Oxford Master Series. As for the first edition, the text is intended for physics undergraduates in their third or later years, so I have kept the presentation and mathematical treatment at a reasonable level. I believed that it was more important to concentrate on the outstanding developments and the burning questions in a very exciting and very wide-ranging subject, rather than spend time and space on long theoretical discussion. At no point have I hesitated to sacrifice mathematical rigour for the sake of brevity and clarity. Again, I have sprinkled a few worked examples throughout the text, which is supplemented with sets of problems at the end of chapters, with answers and some worked solutions at the end of the book.
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