Subject Grouping: Praxis

By Dave Goldberg
Princeton University Press

This book is an excellent source for those interested in learning the basic features of the Standard Model (SM) of particle physics – also known as the Glashow–Weinberg–Salam (GSW) model – without many technical details. It is a remarkably accessible book that can be used for self learning by advanced undergraduates and beginning graduate students. All the basic building blocks are provided in a self-contained manner, so that the reader can acquire a good knowledge of quantum mechanics and electromagnetism before reaching the boundaries of the SM, which is the theory that best describes our knowledge of the fundamental interactions.

The topics that the book deals with include special relativity, basic quantum field theory and the action principle, continuous symmetries and Noether’s theorem, as well as basic group theory – in particular, the groups needed in the SM: U(1), SU(2) and SU(3). It also covers the relativistic treatment of fermions through the Dirac equation, the quantisation of the electromagnetic field and a first look at the theory of gauge transformations in a familiar context. This is followed by a reasonable account of quantum electrodynamics (QED), the most accurate theory tested so far. The quantisation rules are reviewed with clarity and a number of useful and classic computations are presented to familiarise the reader with the technical details associated with the computation of decay rates, scattering amplitudes, phase-space volumes and propagators. The book also provides an elementary description of how to construct and compute Feynman rules and diagrams, which are later applied to electron–electron scattering and electron–positron annihilation, and how the latter relates to Compton or electron–photon scattering. This lays the basic computational tools to be used later in the sections about electroweak and strong interactions.

At this point, before starting a description of the SM per se, the author briefly describes the historical Fermi model and then presents the main actors. The reader is introduced to the lepton doublet (including the electron, the muon, the tau and their neutrinos), the weak charged and neutral currents, and the vector bosons that carry the weak force (the Ws and the Z). This is followed by an analysis of electroweak unification and the introduction of the weak angle, indicating how the electromagnetic interaction sits inside the weak isospin and hypercharge. Then, the author deals with the quark doublets and the symmetry breaking pattern, using the Brout–Englert–Higgs mechanism, which gives mass to the vector bosons and permits the accommodation of masses for the quarks and leptons. We also learn about the Cabibbo–Kobayashi–Maskawa mixing matrix, neutrino oscillations, charge and parity (CP) violation, the solar neutrino problem, and so on. To conclude, the author presents the SU(3) gauge theory of the strong interactions and provides a description of some theories that go beyond the SM, as well as a short list of important open problems. All this is covered in just over 250 pages: a remarkable achievement. In addition, the book includes many interesting and useful computations.

This work is a very welcome addition to the modern literature in particle physics and I certainly recommend it, in particular for self study. I hope, though, that in the second edition the correct Weinberg is portrayed on p184… an extremely hilarious blunder.

By Don S Lemons
Cambridge University Press

Dimensional analysis is a mathematical technique that allows one to deduce the relationship between different physical quantities from the dimensions of the variables involved in the system under study. It provides a method to simplify – when possible – the resolution of complex physical problems.

This short book provides an introduction to dimensional analysis, covering its history, methods and formalisation, and shows its application to a number of physics and engineering problems. As the author explains, the foundation principle of dimensional analysis is essentially a more precise version of the well known rule against “adding apples and oranges”; nevertheless, the successful application of this technique requires physical intuition and some experience. Most of the time it does not lead to the solution of the problem, but it can provide important hints about the direction to take, constraints on the relationship between physical variables and constants, or a confirmation of the correctness of calculations.

After a chapter covering the basics of the method and some historical notions about it, the book offers application examples of dimensional analysis in several areas: mechanics, hydrodynamics, thermal physics, electrodynamics and quantum physics. Through the solution of these real problems, the author shows the possibilities and limitations of this technique. In the final chapter, dimensional analysis is used to take a few steps in the direction of uncovering the dimensional structure of the universe.

Aimed primarily at physics and engineering students in their first university courses, it can also be useful to experienced students and professionals. Being concise and providing problems with solutions at the end of each chapter, the book is ideal for self study.

By Volker Schomerus
Cambridge University Press

This textbook aims to provide a concise introduction to string theory for undergraduate and graduate students.

String theory was first proposed in the 1960s and has become one of the main candidates for a possible quantum theory of gravity. While going through alternate phases of highs and lows, it has influenced numerous areas of physics and mathematics, and many theoretical developments have sprung from it.

It was the intention of the author to include in the book just the fundamental concepts and tools of string theory, rather than to be exhaustive. As Schomerus states, there are already various textbooks available that cover this field in detail, from its roots to its most modern developments, but these might be dispersive and overwhelming for students approaching the topic for the first time.

The volume is composed of a brief historical introduction and two parts, each including various chapters. The first part is dedicated to the dynamics of strings moving in a flat Minkowski space. While these string theories do not describe nature, their study is helpful to understand many basic concepts and constructions, and to explore the relation between string theory and field theory on a two-dimensional “world”.

The second part deals with string theories for four-dimensional physics, which can be relevant to the description of our universe. In particular, the motion of superstrings on backgrounds in which some of the dimensions are curled up is studied (this phenomenon is called compactification). This part, in turn, includes three sections devoted to as many subtopics.

First, the author discusses conformal field theory, also dealing with the SU(2) Wess–Zumino–Novikov–Witten model. Then, he passes on to treat Calabi–Yau spaces and the associated string compactification. Finally, he focuses on string dualities, giving special emphasis to the AdS/CFT correspondence and its application to gauge theory.

By Christian Fabjan, Thomas Taylor, Daniel Treille and Horst Wenninger (eds.)
World Scientific

This book, the 27th volume in the “Advanced Series on Directions in High Energy Physics”, presents a robust and accessible summary of 60 years of technological development at CERN. Over this period, the foundations of today’s understanding of matter, its fundamental constituents and the forces that govern its behaviour were laid and, piece by piece, the Standard Model of particle physics was established. All this was possible thanks to spectacular advances in the field of particle accelerators and detectors, which are the focus of this volume. Each of the 12 chapters is built using contributions from the physicists and engineers who played key roles in this great scientific endeavour.

After a brief historical introduction, the story starts with the Synchrocyclotron (SC), CERN’s first accelerator, which allowed – among other things – innovative experiments on pion decay and a measurement of the anomalous magnetic dipole moment of the muon. While the SC was a development of techniques employed elsewhere, the Proton Synchroton (PS), the second accelerator constructed at CERN and now the cornerstone of the laboratory’s accelerator complex, was built using the new and “disruptive” strong-focusing technique. Fast extraction from the PS combined with the van der Meer focussing horn were key to the success of a number of experiments with bubble chambers and, in particular, to the discovery of the weak neutral current using the large heavy-liquid bubble chamber Gargamelle.

The book goes on to present the technological developments that led to the discovery of the Higgs boson by the ATLAS and CMS collaborations at the LHC, and the study of heavy-quark physics as a means to understand the dynamics of flavour and the search for phenomena not described by the SM. The taut framework that the SM provides is evident in the concise reviews of the experimental programme of LEP: the exquisitely precise measurements of the properties of the W and Z bosons, as well as of the quarks and the leptons – made by the ALEPH, DELPHI, OPAL and L3 experiments – were used to demonstrate the internal consistency of the SM and to correctly predict the mass of the Higgs boson. An intriguing insight into the breadth of expertise required to deliver this programme is given by the discussion of the construction of the LEP/LHC tunnel, where the alignment requirements were such that the geodesy needed to account for local variations in the gravitational potential and measurements were verified by observations of the stars.

The rich scientific programme of the LHC and of LEP before it have their roots in the systematic development of the accelerator and detector techniques. The accelerator complex at CERN has grown out of the SC.

The book concisely presents the painstaking work required to deliver the PS, the Intersecting Storage Rings (ISR) and the Super Proton Synchrotron (SPS). Experimentation at these facilities established the quark-parton model and quantum chromodynamics (QCD), demonstrated the existence of charged and neutral weak currents, and pointed out weaknesses in our understanding of the structure of the nucleon and the nucleus. The building of the SPS was expedited by the decision to use single-function magnets that enabled a staged approach to its construction. The description of the technological innovations that were required to realise the SPS includes the need for a distributed, user-friendly control-and-monitoring system. A novel solution was adopted that exploited an early implementation of a local-area network and for which a new, interpretative programming language was developed.

The book also describes the introduction of the new isotope separation online technique, which allows highly unstable nuclei to be studied, and its evolution into research on nuclear matter in extreme conditions at ISOLDE and its upgrades. The study of heavy-ion collisions in fixed target experiments at the SPS collider and now in the ALICE experiment at the LHC, has its roots in the early nuclear-physics programme as well. The SC, and later the PS, were ideal tools to create the intense low-energy beams used to test fundamental symmetries, to search for rare decays of hadrons and leptons, and to measure the parameters of the SM.

Reading this chronicle of CERN’s outstanding record, I was struck by its extraordinary pedigree of innovation in accelerator and detector technology. Among the many examples of groundbreaking innovation discussed in the book is the construction of the ISR which, by colliding beams head on, opened the path to today’s energy

frontier. The ISR programme created the conditions for pioneering developments such as the multi-wire proportional chamber, and the transition radiation detector as well as large-acceptance magnetic spectrometers for colliding-beam experiments. Many of the technologies that underpin the success of the proton–antiproton (Spp S) collider, LEP and the LHC, were innovations pioneered at the ISR. For example, the discovery of the W and Z bosons at the Spp S relied on the demonstration of stochastic cooling and antiproton accumulation. The development of these techniques allowed CERN to establish its antiproton programme, which encompassed the search for new phenomena at the energy frontier, as well as the study of discrete symmetries using neutral kaons at CPLEAR and the detailed study of the properties of antimatter.

The volume includes contributions on the development of the computing, data-handling and networking systems necessary to maximise the scientific output of the accelerator and detector facilities. From the digitisation and handling of bubble- and spark-chamber images in the SC era, to the distributed processing possible on the worldwide LHC computing grid, the CERN community has always developed imaginative solutions to its data-processing needs.

The book concludes with thoughtful chapters that describe the impact on society of the technological innovations driven by the CERN programme, the science and art of managing large, technologically challenging and internationally collaborative projects, and a discussion of the R&D programme required to secure the next 60 years of discovery.

The contributions from leading scientists of the day collected in this relatively slim book document CERN’s 60-year voyage of innovation and discovery, the repercussions of which vindicate the vision of those who drove the foundation of the laboratory – European in constitution, but global in impact. The spirit of inclusive collaboration, which was a key element of the original vision for the laboratory, together with the aim of technical innovation and scientific excellence, are reflected in each of the articles in this unique volume.

By Stephen Peggs and Todd Satogata
Cambridge University Press

This concise book provides an overview of accelerator physics, a field that has grown rapidly since its inception and is progressing in many directions. Particle accelerators are becoming more and more sophisticated and rely on diverse technologies, depending on their application.

With a pedagogical approach, the book presents both the physics of particle acceleration, collision and beam dynamics, and the engineering aspects and technologies that lay behind the effective construction and operation of these complex machines. After a few introductory theoretical chapters, the authors delve into the different components and types of accelerators: RF cavities, magnets, linear accelerators, etc. Throughout, they also show the connections between accelerator technology and the parallel development of computational capability.

This text is aimed at university students at graduate or late undergraduate level, as well as accelerator users and operators. An introduction to the field, rather than an exhaustive treatment of accelerator physics, the book is conceived to be self-contained (to a certain extent) and to provide a strong starting point for more advanced studies on the topic. The volume is completed by a selection of exercises at the end of each chapter and an appendix with important formulae for accelerator design.

By Claude A Pruneau
Cambridge University Press

Also available at the CERN bookshop

Since the analysis of data from physics experiments is mainly based on statistics, all experimental physicists have to study this discipline at some point in their career. It is common, however, for students not to learn it in a specific advanced university course but in bits and pieces during their studies and subsequent career.

This textbook aims to present all of the basic statistics tools required for data analysis, not only in particle physics but also astronomy and any other area of the physical sciences. It is targeted towards graduate students and young scientists and, since it is not intended as a text for mathematicians or statisticians, detailed proofs of many of the theorems and results presented are left out.

After a philosophical introduction on the scientific method, the text is presented in three parts. In the first, the foundational concepts and methods of probability and statistics are provided, considering both the frequentist and Bayesian interpretations. The second part deals with the basic and most commonly used advanced techniques for measuring particle-production cross-sections, correlation functions and particle identification. Much attention is also given to the notions of statistical and systematic errors, as well as the methods used to unfold or correct data for the instrumental effects associated with measurements. Finally, in the third section, introductory techniques in Monte Carlo simulations are discussed, focusing on their application to experimental data interpretation.

By Govert Schilling
The Belknap Press of Harvard University Press

In February 2016 the LIGO and Virgo collaborations announced the first detection of gravitational waves from the collision of two black holes. It was a splendid result for a quest that started about five decades ago with the design and construction of small prototypes of laser interferometers. Since this first discovery, at least five other binary black-hole mergers have been found and gravitational waves from two colliding neutron stars have also been detected. Gravitational-wave science is now booming, literally, and will continue to do so for a long time. The upcoming observational progress in this field will impact the development of astrophysics, cosmology and, perhaps, particle physics.

Govert Schilling is an award-winning science journalist with a special interest in astronomy and space science. In this book, he guides the reader through the development of gravitational-wave astronomy, from its very origin deep in the early days of general relativity up to the first LIGO discovery. He does so, not only by delving into the key moments of this wonderful piece of history, but also by explaining the main physical and engineering ideas that made it possible.

Moreover, Schilling does a very good job discussing the scientific context in which these events and ideas arose. Far from being a mere collection of events, the book offers the reader a journey that goes beyond its title, exploring and connecting topics such as the cosmic-microwave background and its polarisation, radioastronomy and pulsars, supernovae, primordial inflation, gamma-ray bursts and even dark energy. In addition, the last few chapters of the book discuss the science that may come next, when new interferometers will join LIGO and Virgo in this adventure, observing the sky from Earth (e.g. KAGRA) and space (LISA).

The book clearly aims to target a non-specialist readership and will surely be enjoyed by people lacking a prior knowledge of astrophysics, gravitational waves or cosmology. However, this does not mean that readers more well-versed in these topics will find the book uninspiring. Schilling addresses the reader in a direct, entertaining, almost colloquial manner, managing to explain complex concepts in a few paragraphs while keeping the science sound. Besides, the book gives an interesting (and sometimes surprising) glimpse into the lives, aspirations and mutual interactions of the scientific pioneers in the field of gravitational waves.

If an objection had to be found, it would be that in the first chapter the author belittles general relativity by introducing it as “the theory behind [the movie] Interstellar”. If this scares you, read on and fear nothing. As always happens, science outshines fiction, and the rest of the book proves why this is so.

By Paul Charbonneau
Princeton University Press

This book aims to introduce readers to the study of complex systems with the help of simple computational models. After showing how difficult it is to define complexity, the author explains that complex systems are an idealisation of naturally occurring phenomena in which the macroscopic structures and patterns generated are not directly controlled by processes at the macroscopic level but arise instead from dynamical interactions at the microscopic level. This kind of behaviour characterises a range of natural phenomena, from avalanches to earthquakes, solar flares, epidemics and ant colonies.

In each chapter the author introduces a simple computer-based model for one such complex phenomenon. As the author himself states, such simplified models wouldn’t be able to reliably foresee the development of a real natural phenomenon, thus they are to be taken as complementary to conventional approaches for studying such systems.

Meant for undergraduate students, the book does not require previous experience in programming and each computational model is accompanied by Python code and full explanations. Nevertheless, students are expected to learn how to modify the code to tackle the problems included at the end of each chapter. Three appendices provide a review of Python programming, probability density functions and other useful mathematical tools.

By Roger Penrose
Princeton University Press

Also available at the CERN bookshop

The well-known mathematician and theoretical physicist Roger Penrose has produced another popular book, in which he gives a critical overview of contemporary fundamental physics. The main theme is that modern theoretical physics is afflicted by an overdose of fashion, faith and fantasy, which supposedly has led recent research astray.

There are three major parts of the book to which these three f-words relate, corresponding one-to-one with some of the most popular research areas in fundamental physics. The first part, labelled “fashion”, deals with string theory. “Faith” refers to the general belief in the correctness of quantum mechanics, while “fantasy” is the verdict for certain scenarios of modern cosmology.

The book starts with an overview of particle physics as a motivation for string theory and quickly focuses on its alleged shortcomings, most notably extra dimensions. Well-known criticisms, for instance linked to the multitude of solutions (“landscape of vacua”) of string theory or the postulate of supersymmetry, follow in due course. This material is mostly routine, but there are also previously unheard of concerns such as the notion of “too much functional freedom” or doubts about the decoupling of heavy string states (supposedly excitable, for example from the orbital kinetic energy of Earth).

Next the book turns to quantum mechanics and gives an enjoyable introduction to some of the key notions, such as superposition, spin, measurement and entanglement. The author emphasises, with great clarity, some subtle points such as how to understand the quantum mechanical superposition of space–times. In doing so, he raises some concerns and argues – quite unconventionally – that, to resolve them, it is necessary to modify quantum mechanics. In particular he asks that the postulate of linearity should be re-assessed in the presence of gravity.

The fantasy section gives an exposition of the key ideas of cosmology, in particular of all sorts of scenarios of inflation, big bang, cyclic universes and multiverses. This is all very rewarding to read, and particularly brilliant is the presentation of cosmological aspects of entropy, the second law of thermodynamics and the arrow of time. I consider this third section as the highlight of the book. The author does not hide his suspicion that many of these scenarios should not be trusted and dismisses them as crazy – while saying, as if with a twinkle in the eye: not crazy enough!

There is a brief, additional, final section that has a more personal and historical touch, and which tries to make a case for Penrose’s own pet theory: twistor theory. One cannot but feel that some of his resentment against string theory stems from a perceived under-appreciation of twistor theory. In particular, the author admits that his aversion to string theory comes almost entirely from its purported extra dimensions, whereas twistors work primarily in four dimensions.

This touches upon a weak point of the book: the author argues entirely from the direction of classical geometry, and so shares a fixation with extra dimensions in string theory with many other critics. What Penrose misses, however, is that these provide an elegant way to represent certain internal degrees of freedom (needed matter fields). But this is by no means generic – on the contrary, most string backgrounds are non-geometric. For example, some are better described by a bunch of Ising models with no identifiable classical geometry at all, so the agony of how to come to grips with such “compactified” dimensions turns into a non-issue. The point is that due to quantum dualities, there is, in general, no unambiguous objective reality of string “compactification” spaces, and criticism that does not take this “stringy quantum geometry” properly into account is moot.

Somewhat similar in spirit is the criticism of quantum mechanics, which according to Penrose should be modified due to an alleged incompatibility with gravity. Today most researchers would take the opposite point of view and consider quantum mechanics as fundamental, while gravity is a derived, emergent phenomenon. This viewpoint is strongly supported by the gauge-gravity duality and its recent offspring in terms of space–time geometry arising via quantum entanglement.

All-in-all, this book excels by covering a huge range of concepts from particle physics to quantum mechanics to cosmology, presented in a beautifully clear and coherent way (spiced up with many drawings), by an independent and truly deep-thinking master of the field. It also sports a considerable number of formulae and uses mathematical concepts (like complex analysis) that a general audience would probably find difficult to deal with; there are a number of helpful appendices for non-experts, though.

Thus, Fashion, Faith and Fantasy in the New Physics of the Universe seems to be suitable for both physics students and experienced physicists alike, and I believe that either group will profit from reading it, if taken with a pinch of salt. This is because the author criticises contemporary fundamental theories through his personal view as a classical relativist, and in doing so falls short when taking certain modern viewpoints into account.

By Vladimir Zelevinsky and Alexander Volya Wiley

This new textbook of nuclear physics aims to provide a review of the foundations of this branch of physics as well as to present more modern topics, including the important developments of the last 20 years. Even though well-established textbooks exist in this field, the authors propose a more comprehensive essay for students who want to go deeper both in understanding the basic principles of nuclear physics and in learning about the problems that researchers are currently addressing. Indeed, a renewed interest has lately revitalised this field, following the availability of new experimental facilities and increased computational resources.

Another objective of this book, which is based on the lectures and teaching experience of the authors, is to clarify, at each step, the relationship between theoretical equations and experimental observables, as well as to highlight useful methods and algorithms from computational physics.

The last few chapters cover topics not normally included in standard courses of nuclear physics, and reflect the scientific interests – and occasionally the point of view – of the authors. Many problems are also provided at the end of each chapter, and some of them are fully solved.

Compiled by Virginia Greco, CERN.