Customer Reviews

Drawing Theories Apart: The Dispersion of Feynman Diagrams in Postwar Physics

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This is a very engaging book on at least two different levels: as a book about history, and as a book about physics.

The book is an early adopter of a couple of new and intriguing techniques in history of science. Instead of trying to identify theories or paradigms, it focuses on physicists' "paper tools" --the techniques they used for calculations. Also, it emphasizes the importance of pedagogy -- a subject's transmission through textbooks, clusters of professors/postdocs/grad students and, importantly in this case, informal contact.

Feynman introduced his diagrams at a small, private conference in spring 1948. He didn't publish about them until September 1949; but by then they were already widely used in studying quantum electrodynamics, albeit not well-understood. Kaiser traces the roles of Freeman Dyson and a cadre of postdocs from Princeton's IAS in spreading the diagrams on both sides of the Atlantic. As each researcher pieced together his (or occasionally her) own understanding of the diagrams, he transmitted it -- together with many idiosyncrasies -- to his students. A neat figure in the book compares the styles of diagram used by professors and students at major universities. Students tended to follow their teachers, but no two institutions had the same style. (Kaiser also traces the spread of the diagrams in Japan and Russia, two physics communities that were largely isolated from Western researchers.)

The result was a Balkanization of styles and interpretations of the diagrams. This had already begun with Dyson's first articles in February 1949. Feynman had viewed the diagrams as intuitively depicting the behavior of particles in spacetime. Kaiser connects the diagrams' enduring appeal to their similarity to particle tracks in bubble-chamber photos, which makes a viewer feel that the diagrams are a realistic picture of what's going on. Dyson, on the other hand, regarded them as a geometric algorithm for keeping track of terms in a perturbative expansion in QED; he was also the first to promote viewing them in an abstract, topological way.

These centrifugal tendencies became elaborated and diversified in the 1950s and 1960s. All sorts of new diagrams sprung up, with different kinds of lines, arrows, geometries and "blobs" -- but eventually all were called "Feynman diagrams". The uses of the diagrams also diverged, from being a tool of quantum field theory to being a tool for its (attempted) overthrow. Among many other fascinating stories, Kaiser describes the UC Berkeley "particle democracy" movement, which used geometrical permutations of the diagrams to make a case that the distinction between "elementary" and "composite" particles is false. (By similar means, the school of Lev Landau came to regard diagrams as more fundamental than field theory.)

Kaiser does a great job of providing the historical context of what problems each group was trying to address, including adapting the diagrams to studying QED in condensed matter as well as other QFTs, such as the strong interaction. Along the way, you'll learn a little about Regge theory, pomerons, the Mandelstam representation, the analytical S-matrix, and other approaches to QFT that still surface today in corners of the arXiv. You won't find these developments described in other histories of the period, such as Schweber's "QED" or Pais's ultra-terse "Inward Bound". Kaiser's book is indispensible for understanding diagrams in the physics literature from the 1950s and 1960s and perhaps later. (And since it's much shorter than Schweber and less oracular than Schwinger, it's a good introduction to the second half of the Dover collection of QED papers, which Schwinger edited and introduced.)

Readers more interested in QFT than in history might be put off by Kaiser's at times dry style, and especially by the critical theory-tinged first chapter (influenced by the science studies ramblings of Bruno Latour et al.) But don't be put off. While much of the history Kaiser describes has been forgotten, it survives in the eclectic style of "Feynman diagrams" you'll find in many textbooks today -- e.g., Itzykson & Zuber, Ryder, Mattuck, and A. Zee's recent "Nutshell", which mixes diagrammatic styles with an especially breezy abandon. In all of these, turn a few pages past the dutiful description of the 1949 Feynman-Dyson rules and you'll start seeing diagrams about QCD, or diagrams with blobs or double-arrows or other innovations, most of which won't be explained systematically. Kaiser's book will help you to decipher some of these diagrammatic puzzles. Even better, it may make you sensitive to some of the uses, interpretations, and ambiguities of diagrams that you might never have considered otherwise.

This is one of the best history of physics books I've read. Kaiser has a very engaging style of writing and explains technical physical concepts well. Those talents, together with the quirky personalities involved, and the many often humorous quotes from physicists scattered throughout, mean that even the lay reader would be able to enjoy this book. It's far more accessible than, for example, Andrew Pickering's Constructing Quarks. It's also far more entertaining and less loaded with jargon.

Even more impressively, the accessible style doesn't detract from the quality of research presented. With his detailed accounts of the myriad, often mutually contradictory applications of field theory and Feynman diagrams, Kaiser makes a strong case against theory-centric philosophy of science and for a more Cartwrightian stance. He also does an excellent job of describing contrasting strands of methodologies, such as Dyson's use of Feynman diagrams primarily as a bookkeeping device in mathematically rigorous field theory versus Feynman's own much more relaxed and sloppy use of the diagrams. He has a convincing presentation of the sociology involved in the spread of Feynman diagrams -- unlike many sociology of science works that are steeped in social constructionist jargon, this was all done in extremely accessible language and kept me turning the pages -- the prose was not dry at all.

Historical books are generally far down my list of books to read but this was a rare gem. Granted, I have a strong interest in nuclear/hep physics which certainly helps but I could see anyone with some basic grounding in math/science enjoying this book. It really is fascinating to look at the myriad ways in which the diagrams not only spread, but evolved and how they have become ubiquitous. The bibliography is quite extensive and at some point I will try to find some of the source material to look at too. Definitely a geek page turner.

For physicists, this book makes engaging reading. Feynman diagrams are now well established, and have been so for decades. They give crucial understanding to some very intricate equations in high energy physics.

Kaiser has performed some indepth historical research on the early postwar years. When Feynman had his seminal insights into how these graphical techniques could simplify a tangle of equations. Today, with a pervasive web and instantaneous email between researchers across the globe, it is a very different environment. Then, a compelling idea still primarily had to be transmitted by the traditional method of inperson presentations, like seminars and conferences and actual letters.

The book is as much about the sociology of science as it is about the physics devised by Feynman. Granted, key sections may be intelligible only to physicists. These delve into the physics and equations of propagators and Hamiltonians in quantum mechanics. But most of the book can be gainfully read by non-physicists, who might want more details about Richard Feynman's life.

Storied names of 20th century physicists are also generously scattered throughout the book. Bethe [Feynman's PhD advisor], Dyson, Gell-Mann, Salam and others.

A fantastic book. With too many words sometimes, but really good.
It has 496 pages, not the number indicated in the Amazon page.