Subject Grouping: Praxis

By Johann Rafelski
Springer

Also available at the CERN bookshop

This monograph on special relativity (SR) is presented in a form accessible to a broad readership, from pre-university level to undergraduate and graduate students. At the same time, it will also be of great interest to professional physicists.

Relativity Matters has all the hallmarks of becoming a classic with further editions, and appears to have no counterpart in the literature. It is particularly useful because at present SR has become a basic part not only of particle and space physics, but also of many other branches of physics and technology, such as lasers. The book has 29 chapters organised in 11 parts, which cover topics from the basics of four-vectors, space–time, Lorentz transformations, mass, energy and momentum, to particle collisions and decay, the motion of charged particles, covariance and dynamics.

The first half of the book derives basic consequences of the SR assumptions with a minimum of mathematical tools. It concentrates on the explanation of apparently paradoxical results, presenting and refuting counterarguments as well as debunking various incorrect statements in elementary textbooks. This is done by cleverly exploiting the Galilean method of a dialogue between a professor, his assistant and a student, to bring out questions and objections.

The importance of correctly analysing the consequences for extended and accelerating bodies is clearly presented. Among the many “paradoxes”, one notes the accelerating rocket problem that the late John Bell used to tease many of the world’s most prominent physicists with. Few of them provided a perfectly satisfactory answer.

The second half of the book, starting from part VII, covers the usual textbook material and techniques at graduate level, illustrated with examples from the research frontier. The introductions to the various chapters and subsections are still enjoyable for a broader readership, requiring little mathematics. The author does not avoid technicalities such as vector and matrix algebra and symmetries, but keeps them to a minimum. However, in the parts dealing with electromagnetism, the reader is assumed to be reasonably familiar with Maxwell’s equations.

There are copious concrete exercises and solutions. Throughout the book, indeed, every chapter is complemented by a rich variety of problems that are fully worked out. These are often used to illustrate quantitatively intriguing topics, from space travel to the laser acceleration of charged particles.

An interesting afterword concluding the book discusses how very strong acceleration becomes a modern limiting frontier, beyond which SR in classical physics becomes invalid. The magnitude of the critical accelerations and critical electric and magnetic fields are qualitatively discussed. It also briefly analyses attempts by well-known physicists to side-step the problems that arise as a consequence.

Relativity Matters is excellent as an undergraduate and graduate textbook, and should be a useful reference for professional physicists and technical engineers. The many non-specialist sections will also be enjoyed by the general, science-interested public.Torleif Ericson, CERN

By Alberto A García-Díaz
Cambridge University Press

As stated by the author himself, this book is the result of many years of work and has the purpose of providing a comprehensive, but concise, account of exact solutions in three-dimensional (or 2+1) Einstein gravity. It presents the theoretical frameworks and the general physical and geometrical characteristics of each class of solutions, and includes information about the researchers who discovered or studied them.

These solutions are identified and ordered on the basis of their geometrical invariant properties, their symmetries and their algebraic classifications, or according to their physical nature. They are also examined from different perspectives.

Emphasis is given to solutions to the Einstein equation in the presence of matter and fields, such as: point particle solutions, perfect fluids, dilatons, inflatons and cosmological space-times.

The second part of the book discusses solutions to vacuum topologically massive gravity with a cosmological constant.

Overall, this text serves as a thorough catalogue of exact solutions in (2+1) Einstein gravity and is a very valuable resource for graduate students, as well as researchers in gravitational physics.

by Lucy Kirkwood
National Theatre, London 18 July–28 September 2017

Lucy Kirkwood’s play Mosquitoes is an ambitious piece of theatre. It combines the telling of an eclectic family drama with the asking of a variety of questions ranging from personal relationships to the remit of science. Mosquitoes tells the story of CERN scientist Alice (Olivia Williams), and the fractious relationship she has with her sister Jenny (Olivia Colman). After working for 11 years at CERN on the French–Swiss border, Alice is visited by Jenny just as work on discovering the Higgs boson is nearing its peak. Conflict between Jenny and Alice’s challenged son, Luke (Joseph Quinn), drives much of the plot. Domestic scenes between these three characters are interspersed with glimpses of Luke’s absent father, who momentarily turns the theatre into a planetarium while waxing lyrical over the science which the play is set against.

The spectacle of these brief moments is a highlight of the play; contrasting wonderfully with the often mundane lives of the characters. Kirkwood also makes a poignant contrast between the characters’ personal and professional lives. Alice, despite exuding a certain confidence in her professional life as a scientist, often struggles to relate personally to those around her. Chief amongst those is her son Luke who, despite showing the occasional interest in his mother’s work, is ultimately critical of it for a number or reasons. He questions the environmental impact of what she is doing, believing that the LHC poses existential risks. He also frequently bemoans his mother’s commitment to her work, which he believes comes at the expense of himself. Through the play, it becomes apparent that Luke and his mother previously lived in the UK, and that he was made to follow her to Switzerland, but he would like to go back to England.

These personal relationships are played out in front of the sisters’ ailing mother Karen (Amanda Boxer). A former physicist herself now suffering from dementia, Karen frequently laments missing out on her chances at winning a Nobel Prize. Karen’s character, who provides the audience with a glimpse of her daughter Alice’s future, adds a sense of futility to Alice’s work.

Overall, Mosquitoes – the title coming from a line of dialogue in which protons smashing in the Large Hadron Collider are compared to mosquitoes hitting each other head on – is a stunning piece of work. Not just for the way it weaves together story lines to explore a range of complex questions, but also for the immensely high quality of acting talent which it boasts. This is bettered only by the faultless light, sound, and set design, which complement each other perfectly during the play’s most dramatic moments.

By Abhay Ashtekar and Jorge Pullin (eds.)
World Scientific

This book, which is part of the “100 Years of General Relativity” series of monographs, aims to provide an overview of the foundations and recent developments of loop quantum gravity (LQG).

This is a theory that merges quantum mechanics and general relativity in an effort to unify gravity with the other three fundamental forces. In the approach of LQG, space–time is not a continuum, but it is quantised, and is considered as a dynamic entity. Different from string theory, loop quantum gravity is a “background-independent” theory, which aims to explain space and time instead of being plugged into an already existing space–time structure.

The book comprises eight chapters, distributed in three parts. The first is a general introduction that sets the scene and anticipates what will be discussed in detail in the following sections. The second part, comprising five chapters, introduces the conceptual, mathematical and physical foundation of LQG. In part three, the application of this theory to cosmology and black holes is discussed, also introducing predictions that might be testable in the foreseeable future.

Written by young theoretical physicists who are expert in the field, this volume is meant both to provide an introduction to the field and to offer a review of the latest developments, not discussed in many other existing books, for senior researchers. It will also appeal to scientists who do not work directly on LQG but are interested in issues at the interface of general relativity and quantum physics.

By Ivar Giaever
World Scientific

At the end of his last semester studying mechanical engineering at the Norwegian Institute of Technology, Ivar Giaever gained a grade of 3.5 for a thesis on the efficiency of refrigeration machines – just a little better than the 4.0 needed to pass. The thesis had been hastily written as the machines worked badly, and he and his friend had had little time to collect their data. But they both scraped through and, as Giaever writes, “maybe sometimes life is a little bit fair after all?”.

It’s a reference to the opening words of his light-hearted autobiography: “Life is not fair, and I, for one, am happy about that.” The title sounds provocative, but

the book is a reflection on how life’s little twists and turns can have extremely important consequences.

Giaever calls this “luck” and admits that he has had more than his share of it – from relatively humble beginnings in Norway to a Nobel prize and beyond.

In many respects Giaever had been a “bad” student. Good at cards, billiards, chess – and drinking – he had little interest in mechanical engineering. He finished with a grade of 4.0 in both physics and mathematics; but had at least married Inger, his long-time sweetheart.

His first job was at the patent office in Oslo, but apartments were hard to find, so the couple decided to emigrate to Canada. A few twists led Giaever to General Electric (GE), where he had the chance to study again through the company’s “A, B and C” courses.

This second chance to learn proved pivotal. Seeing how the studies related to GE’s production of generators, motors and such like, made learning exciting, and Giaever graduated as the best student on the A course. But GE in Canada offered only the A course and, eager to learn more, he moved to GE’s Research Laboratory in Schenectady in the US.

There he completed the B and C courses, and also began studying for a master’s degree in physics at the Rensselaer Polytechnic Institute (RPI). He was to remain with GE for the next 30 years, after being offered a permanent job, even though he did not yet have a PhD.

As a fully-fledged member of the research lab, Giaever needed a project. John Fisher proposed that he look into quantum mechanical tunnelling between thin films, which Giaever went on to do with great success in 1959.

Then, during his studies at RPI, he learned about the new Bardeen–Cooper–Schrieffer (BCS) theory of superconductivity, which predicted the appearance of a forbidden energy gap near the Fermi level when a metal becomes superconducting. Giaever realised that he could measure this gap using his tunnelling apparatus, and so provide crucial verification of the BCS theory. He also realised that tunnelling between two superconductors with different energy gaps would produce a negative resistance, and could allow for active devices such as amplifiers. He worried that if he talked about his work, others would realise this before he had done the relevant experiment.

To his surprise nobody did, hence his comment to his family: “I am the smartest man I know!”. His children thought he was being big-headed, but in 1973 the whole family went with him to Stockholm when he was rewarded with a share of the Nobel Prize in Physics in 1973 for his work on tunnelling in superconductors.

Giaever, of course, covers much more of his life story in this book. There is little technical detail, but a plethora of anecdotes that provide fascinating insight into a person who has made the most of his life.

Two impressions stand out: he is lucky to have found in Inger a partner with whom he has been able to share his long life; and he is lucky to have had a second chance to study and discover that he is smarter than many people thought.

By Nicholas Manton and Nicholas Mee
Oxford University Press

Ranging from classical to quantum mechanics, from nuclear to particle physics and cosmology, this book aims to provide an overview of various branches of physics in both a comprehensive and concise fashion. As the authors state, their objective is to offer an inspirational tour of fundamental physics that is accessible to readers with a high-school background in physics and mathematics, and to motivate them to delve deeper into the topics covered.

Key equations are presented and their solutions derived, ensuring that each step is clear. Emphasis is also placed on the use of variational principles in physics.

After introducing some basic ideas and tools in the first chapter, the book presents Newtonian dynamics and the application of Newton’s law of gravitation to the motion of bodies in the solar system. Chapter 3 deals with the electromagnetic field and Maxwell’s equations. From classical physics, the authors jump to Einstein’s revolutionary theory of special relativity and the concept of space–time. Chapters 5 and 6 are devoted to curved space, general relativity and its consequences, including the existence of black holes. The other revolutionary idea of the 20th century, quantum mechanics, is discussed in chapters 7 and 8, while chapter 9 applies this theory to the structure and properties of materials, and explains the fundamental principles of chemistry and solid-state physics. Chapter 10 covers thermodynamics, built on the concepts of temperature and entropy, and gives special attention to the analysis of black-body radiation. After an overview of nuclear physics (chapter 11), chapter 12 presents particle physics, including a short description of quantum field theory, the Standard Model with the Higgs mechanism and the recent discovery of its related boson. Chapters 13 and 14 are about astrophysics and cosmology, while the final chapter discusses some of the fundamental problems that remain open.

By Katherine Freese
Princeton University Press

Also available at the CERN bookshop

This book by Katherine Freese, now out in paperback, is aimed at non-professionals interested in dark matter. The hypothesis that the matter in galaxy clusters is dominated by a non-luminous component, and hence is dark, goes back to a paper published in 1933 by the Swiss astronomer Fritz Zwicky, who also coined the term “dark matter”. But it has only been during the last 20 years or so that we have realised that the matter in the universe is dominated by dark matter and that most of it is non-baryonic, i.e. not made of the stuff that makes up all the other matter we know.

The author explains the observational evidence for dark matter and its relevance for cosmology and particle physics, both in a formal scientific context and also based on her personal adventures as a researcher in this field. I especially enjoyed her detailed, well-informed discussion and evaluation of present dark-matter searches.

The book is structured in nine chapters. The first is a personal introduction, followed by a historical account of the growing evidence for dark matter. Chapter 3 discusses our present understanding of the expanding universe, explaining how much of what we know is due to the very accurate observations of the cosmic microwave background. This is followed by a chapter on Big Bang nucleosynthesis, describing how the first elements beyond hydrogen (deuterium, helium-3, lithium and especially helium-4) were formed in the early universe. In the fifth chapter, the plethora of dark-matter candidates – ranging from axions to WIMPS and primordial black holes – are presented. Chapter 6 is devoted to the LHC at CERN: its four experiments are briefly described and the discovery of the Higgs is recounted. Chapters 6 and 7 are at the heart of the author’s own research (the author is a dark-matter theorist and not heavily involved in any particular dark-matter experiments). They discuss the experiments that can be undertaken to detect dark matter, either directly or indirectly or via accelerator experiments. An insightful and impartial discussion of present experiments with tentative positive detections is presented in chapter 8. The final chapter is devoted to dark energy, responsible for the accelerated expansion of the universe. Is it a cosmological constant or vacuum energy with a value that is many orders of magnitude smaller than what we would expect from quantum field theory? Is it a dynamical field or does the beautiful theory of general relativity break down at very large distances?

Even though in some places inaccuracies have slipped in, most explanations are rigorous yet non-technical. In addition to the fascinating subject, the book contains a lot of interesting personal and historical remarks (many of them from the first- or second-hand experience of the author), which are presented in an enthusiastic and funny style. They are one of the characteristics that make this book not only an interesting source of information but also a very enjoyable read.

As a female scientist myself, I appreciated the way the author acknowledges the work of women in science. She presents a picture of a field of research that has been shaped by many brilliant female scientists, starting from Vera Rubin’s investigations of galaxy rotation curves and ending with Elena Aprile’s and Laura Baudis’ lead in the most advanced direct dark-matter searches. It seems to need a woman to do justice to our outstanding female colleagues.

The fact that less than three years after the first publication of the book some cosmological parameters have shifted and some information about recent experiments is already outdated only tells us that dark matter is a hot topic of very active research. I sincerely hope that the author’s gut feeling is correct and the discovery of dark matter is just around the corner.

By A G Wright
Oxford University Press

This volume is a comprehensive handbook aimed primarily at those who use, design or build vacuum photomultipliers. Drawing on his 40 years of experience as a user and manufacturer, the author wrote it to fill perceived gaps in the existing literature.

Photomultiplier tubes (PMTs) are extremely sensitive light detectors, which multiply the current produced by incident photons by up to 100 million times. Since their invention in the 1930s they have seen huge developments that have increased their performance significantly. PMTs have been and still are extensively applied in physics experiments and their evolution has been shaped by the requirements of the scientific community.

The first group of chapters sets the scene, introducing light-detection techniques and discussing in detail photocathodes – important components of PMTs – and optical interfaces. Since light generation and detection are statistical processes, detectors providing electron multiplication are also considered statistical in their operation. As a consequence, a chapter is dedicated to some theory of statistical processes, which is important to choose, use or design PMTs. The second part of the book deals with all of the important parameters that determine the performance of a PMT, each analysed thoroughly: gain, noise, background, collection and counting efficiency, dynamic range and timing. The effects of environmental conditions on performance are also discussed. The last part is devoted to instrumentation, in particular voltage dividers and electronics for PMTs.

Each chapter concludes with a summary and a comprehensive set of references. Three appendices provide additional useful information.

The book could become a valuable reference for researchers and engineers, and for students working with light sensors and, in particular, photomultipliers.

By Jennifer Coopersmith
Oxford University Press

With contagious enthusiasm and a sense of humour unusual in this kind of literature, this book by Jennifer Coopersmith deals with the principle of least action or, to be more rigorous, of stationary action. As the author states, this principle defines the tendency of any physical system to seek out the “flattest” region of “space” – with appropriate definitions of the concepts of flatness and space. This is certainly not among the best-known laws of nature, despite its ubiquity in physics and having survived the advent of several scientific revolutions, including special and general relativity and quantum mechanics. The author makes a convincing case for D’Alembert’s principle (as it is often called) as a more insightful and conceptually fertile basis to understand classical mechanics than Newton’s laws. As she points out, Newton and D’Alembert asked very different questions, and in many cases variational mechanics, inspired by the latter, is more natural and insightful than working in Newton’s absolute space, but it can also feel like using a sledgehammer to crack a peanut.

The book starts with a general and very accessible introduction to the principle of least action. Then follows a long and interesting description of the developments that led to the principle as we know it today. The second half of the book delves into Lagrangian and Hamiltonian mechanics, while the final chapter illustrates the relevance of the principle for modern (non-classical) physics, although this theme is also touched upon several times in the preceding chapters.

An important caveat is that this is not a textbook: it should be seen as complementary to, rather than a replacement for, a standard introduction to the topic. For example, the Euler–Lagrange equation is presented but not derived and, in general, mathematical formulae are kept to a bare minimum in the main text. Coopersmith compensates for this with several thorough appendices, which range from classical textbook-like examples to original derivations. She makes a convincing critique of a famous argument by Landau and Lifshitz to demonstrate the dependence of kinetic energy on the square of the speed, and in one of the appendices she develops an interesting alternative explanation.

Although the author pays a lot of credit to The Variational Principles of Mechanics by Cornelius Lanczos (written in 1949 and re-edited in 1970), hers is a very different kind of book aimed at a different public. Moreover, the author has developed several original and insightful analogies. For example, she remarks upon how smartphones know their orientation: instead of measuring positions and angles with respect to external (absolute) space, three accelerometers in the phone measure tiny motions in three directions of the local gravity field. This is reminiscent of the methods of variational mechanics.

Notations are coherent throughout the book and clearly explained, and footnotes are used wisely. With an unusual convention that is never made explicit, the author graphically warns the reader when a footnote is witty or humorous, or potentially perceived as far-fetched, by putting the text in parenthesis.

My main criticism concerns the frequent references to distant chapters, which entangle the logical flow. This is a book made for re-reading and, as a result, it might be difficult to follow for readers with little previous knowledge of the topic. Moreover, I was rather baffled by the author’s confession (repeated twice) that she was unable to find a quote by Feynman that she is sure to have read in his Lectures. Nevertheless, these minor flaws do not diminish my general appreciation for Coopersmith’s very useful and well-written book.

The first part is excellent reading for anybody with an interest in the history and philosophy of science. I also recommend the book to students in physics and mathematics who are willing to dig deeper into this subject after taking classes in analytical mechanics, and I believe that it is accessible to any student in STEM disciplines. Practitioners in physics from any sub-discipline will enjoy a refresh and a different point of view that puts their tools of the trade in a broader context.