# Bookshelf

25 October 2011

The Pursuit of Quantum Gravity: Memoirs of Bryce DeWitt from 1946 to 2004
By Cécile DeWitt Morette

Springer 2011
Hardback: £31.99 €36.87 $49.95 Bryce DeWitt’s Lectures on Gravitation By Bryce DeWitt (ed. Steven M Christensen) Springer 2011 Paperback: £62.99 €73.80$89.95

Bryce DeWitt made many deep contributions to quantum field theory, general relativity and quantum gravity. He generalized Richard Feynman’s original approach to quantum gravity at the one-loop level, to a fully fledged, all-order quantization of non-abelian gauge theories, including ghosts. The formalism that he developed also transformed the way that we think about quantum field theory, although it took some time before his ideas percolated the community.

The Pursuit of Quantum Gravity is a charming and remarkable book put together by Cécile Morette, who became his wife and was to share his life for more than 50 years. Here we meet the man and his science. It is a remarkable story of vision, passion, independence and determination that led this scientist along such a difficult road, against all odds.

The material in the book is difficult to find elsewhere and it is not only highly informative but also a pleasure to read. For instance, the way that he organized an expedition to Mauritania to check the deflection of light by the Sun and thus verify the results from the 1919 eclipse by Arthur Eddington et al. There are also documents that are not easily accessible elsewhere, such as the essay that won him the first prize of the Gravity Research Foundation in 1953. It is quite remarkable how many aspects of the vision laid out in that paper that he was able to accomplish.

This book makes us aware of how much we owe Bryce DeWitt, and how deep and broad his influence has been. It pays homage to a truly great man – through the words of the person who knew and understood him best.

Back in 1971, he delivered a series of lectures on gravitation at Stanford University, before moving to the University of Texas at Austin. It has taken 40 years for them to be available to the physics community, but finally they are here as Bryce DeWitt’s Lectures on Gravitation, thanks to the efforts of his former student Steven M Christensen. Anyone who has seen the original realizes how grateful we should be to the editor for the large amount of work required in carrying out this task.

These lectures do not represent a standard introduction to the subject but rather DeWitt’s unique way of presenting it. Along with standard topics that include special relativity, continuous groups and Riemannian manifolds, one finds a remarkable treatment of the study of asymptotic fields, the energy–momentum of the gravitational field, and above all the dynamics of the production and propagation of gravitational waves.

Many of the results found here cannot be found in other books or review articles on the subject, despite the number of years that have elapsed since they were presented. Take, for example, the treatment of the angular momentum carried by gravitational waves, where a cursory look at the relevant chapters shows why this book is different. The complexity of the algebra involved requires a combination of tenacity, wizardry and understanding that is difficult to find in any other master of general relativity. DeWitt’s head-on, uncompromising approach is unique.

The book also has high historical value, showing how this maverick maven thought of the subject. It is a great tribute to his scientific legacy.

Luis Álvarez-Gaumé, CERN.

Gravitation: Foundations and Frontiers
Cambridge University Press
Hardback: £50 $85 E-book:$68

The general theory of relativity – the foundation of gravitation and cosmology – may be as widely known today as Newton’s laws were before Einstein proposed their geometric interpretation. That was around 100 years ago, yet many unanswered questions and issues are being revisited from the current perspective, such as: why is gravity described by geometry and why is the cosmological constant so extraordinarily fine-tuned in comparison with the scale of elementary particles?

In an active research field – where the universe at large meets the discoveries in particle physics – there is much need for textbooks based on research that address gravity in depth. Thanu Padmanabhan’s book fills this need well and in a unique way. Within minutes of opening the rich, heavy, full, yet succinctly written 728 pages I realized that this is a new and personal view on general relativity, which leads beyond many excellent standard textbooks and offers a challenging training ground for students with its original exercises and study topics.

In the first 340 pages, the book presents the fundamentals of relativity in an approachable style. Yet, even in this “standard” part the text goes far beyond the conventional framework in preparing the reader in depth for mastering the “frontiers”. The titles of the following chapters speak for themselves: “Black Holes”, “Gravitational Waves”, “Relativistic Cosmology” and “Evolution of Cosmological Perturbations”, all of which address key domains in present-day research. Then, on page 591, the book turns to the quantum frontier and extensions of general relativity to extra dimensions, and to efforts to view it as an effective “emergent” theory.

This research-oriented volume is written in a format that is suitable for a primary text in a year-long graduate class on general relativity, although the lecturer is likely to leave a few of the chapters to self-study. “Padmanabhan” complements the somewhat older offerings of this type, such as “The Big Black Book” (Gravitation by Charles Misner, Kip Thorne and John Wheeler, W H Freeman 1973) or “Weinberg” (Gravitation and Cosmology: Principles and Applications of the General Theory of Relativity, Wiley 1972).

Naturally, this publication differs greatly from “text and no research” offerings, such as Ta-Pei Cheng’s Relativity, Gravitation and Cosmology: A Basic Introduction (OUP 2009) or Ray d’Inverno’s Introducing Einstein’s Relativity (OUP 1992). Any lecturer using these should consider adding “Padmanabhan” as an optional text to offer a wider view to students on what is happening in research today. In comparison with “Hartle” (Gravity: An Introduction to Einstein’s General Relativity, Addison-Wesley 2003), one cannot but admire that “Padmanabhan” does not send the reader to other texts to handle details of computations; what is mentioned is also derived and explained in depth. Of course, “Hartle” is often used in a “first” course on gravity but frankly how often is there a “second” course?

“Padmanabhan” is, as noted earlier, voluminous, making it an excellent value for money because it contains the material of three contemporary books for the price of one. So who should own a copy? Certainly for any good library covering physics, the question is really not if to buy but how many copies. I also highly recommend it to anyone interested in general relativity and related fields because it offers a modern update. Students who have already had a “first” course in the subject and are considering taking up research in this field will find in “Padmanabhan” a self-study text to deepen their understanding. If you are a bookworm like me, you must have it, because it is a great read from start to finish.

Johann Rafelski, University of Arizona.