by Pierre Ramond, Perseus, 0738201162.
Judging by this book, Pierre Ramond must be somebody who spends more time packing his suitcases than travelling. He must therefore be a very well prepared and careful traveller. Two-thirds of Journeys Beyond the Standard Model is devoted to the Standard Model of fundamental particle interactions. However, those first seven chapters contain much more than an introduction. The Standard Model is presented using a modern point of view – the one usually taken by researchers working to extend the theory to a more fundamental level.
The lessons of the first part of the book are of paramount importance in the construction of theories beyond the Standard Model. For instance, emphasis is given to an effective-theory approach, in which higher-dimensional operators are understood as the low -energy manifestation of a fundamental theory emerging at very short distances. The discussion of the approximate symmetries of the fermionic sector (baryon, lepton and flavour symmetries) and Higgs sector (custodial symmetry) not only provides a deeper understanding of the Standard Model structure but clarifies the basic problems encountered in its extensions.
The book requires a previous knowledge of field theory. Nevertheless, the first chapter contains a brief recollection of important results of the spinorial representations of the Lorentz group, of gauge fields with and without spontaneous symmetry breaking, and of group theory. The discussion of group theory, although short, is very lucid and instructive for particle physicists interested in theories beyond the Standard Model. It is written in “Dynkinese”, the group-theoretical language based on Dynkin diagrams. In the Standard Model the group structure is rather simple and the group-theoretical language is a matter of taste. However, research in Grand Unified theories uses Dynkinese, because keeping track of tensorial indices in large group representations is often totally impracticable.
After some history of the Standard Model, its Lagrangian is presented in its full glory. We learn about its astonishing simplicity in terms of principles and its impressive experimental confirmation. One emerges with the conviction that the Standard Model is one of the greatest intellectual achievements of mankind. The discussion in Ramond’s book is clear and complete – one of the best ever published. The studyof the electroweak vacuum is presented with a careful treatment of gauge fixing in theories with spontaneously broken and unbroken gauge symmetry. The book also contains many detailed examples of calculations of Standard Model processes (tree-level decays, loop corrections to electroweak observables and strangeness-changing kaon processes).
A full chapter is devoted to the chiral Lagrangian and its applications at a depth that is unusual for introductory books on the Standard Model. The author is thus able to introduce many concepts (construction of effective theories for strong interactions, non trivial vacuum structure of gauge theories and anomalous global symmetries) frequently used in attempts to formulate theories beyond the Standard Model. Many applications of these concepts are found in the chapter on axions towards the end of the book.
While the presentation of the Standard Model in Ramond’s book is systematic and of extremely high quality, the discussion of theories beyond the Standard Model is more episodic. Indeed, as suggested by the title of the book, Ramond is offering some journeys into the vast territory of new physics; he makes no claim to discuss the complete subject thoroughly.
The first journey describes possible theoretical explanations for neutrino masses, and the experimental evidence for neutrino oscillations in solar and atmospheric neutrino experiments. In the second journey theauthor investigates axion properties and derives their effective interactions with matter and radiation. The third journey presents the minimal supersymmetric extension of the Standard Model.
All three chapters are successful introductions to their respective subjects. More advanced readers may remain dissatisfied with the space allotted to these topics – especially for supersymmetry, a subject by now too vast to be covered in any depth by a single chapter of a book.
Anybody who wants to start a journey beyond the physics of the Standard Model will find this book a wonderful travelling companion. It provides a clear and insightful description of the structure of the Standard Model and gives the necessary tools to approach the frontier research in the domain of new physics.
Ramond’s book is also very timely, because research in particle physics is now moving from the period of consolidation and confirmation of the Standard Model to a period in which both theoretical speculations and experimental activity will focus on understanding deep questions that lie beyond the Standard Model’s predictability, such as the mechanism of electroweak breaking, the origin of masses and the unification of forces.
Imaginative physicists have produced many possible “ultimate” theories to extend the Standard Model. What are now needed are data to test these hypotheses and guide the speculations. There will be much to gain by the unprecedented investigation of nature at distances of less than 10-19m. Considerable understanding of the fundamental principles of physical laws can be revealed by undertaking the journeys described in Pierre Ramond’s book, provided that the traveller invests in the Standard Model groundwork excellently surveyed in the book’s initial chapters.
