String Theory, Yet Another Book

A look at but less than a review of String Theory Demystified by David McMahon.

An extremely popular genre these days is is that of the book which promises an easy road to understanding some subject. The "For Dummies" series is probably the most extensive, but a whole host of competitors are also out there. One that leans technical is the "Demystified" series which sets out to tackle Advanced Calculus, Complex Variables, Quantum Field Theory and String Theory, among many others.

Now these subjects are not really cloaked in mystery. What they are is advanced, in the sense that one needs to master a lot of other material before one can understand them. "For Dummies," "Demystified", and similar titles could probably more accurately be called "A concise introduction to ..." books.

To be sure, there is some variation in the flavors of the genre. At 1200 plus pages, "Java in a Nutshell" can hardly be called concise. Zee's "Quantum Field Theory in a Nutshell" is an idiosyncratic textbook but neither concise nor especially simple, and Kirtsis's "String Theory in a Nutshell" is advanced and only concise by comparison to its even larger competitors.

The "For Dummies" books set a kind of standard. I'm a big fan of Weight Training for Dummies for example, and the subject strikes me as nearly ideal. There are no real prerequisites and the concepts to be mastered are not complex, but they are fairly extensive. Muscles need to be named, described, and located, and a wide variety of weight training machines need to be explained. Add appropriate explanations of proper technique, safety rules, and etiquette and you have material for a two hundred page plus book with large print and lots of pictures. The authors succeed by being well organized, by explaining clearly, and teaching systematically in suitable sized chapters.

Can you do that with string theory? I was initially skeptical, but Lubos Motl's recommendation persuaded me to make the modestly priced purchase. String Theory Demystifyed (hereinafter STD), with its low page count (about 300) and relatively large print has a lot less text than typical ST textbooks. McMahon is not, so far as I can tell, a string theorist.

Anyway, I'm not ready to make a full review, but I did look somewhat closely at chapters four and five. Chapter Four is titled "String Quantization" and goes through covariant quantization and light cone quantization. I found the presentation clear, simple and direct. Of course I can't testify as to accuracy or completeness, you will have to rely on Lubos for that sort of thing. Chapter Five is called "Conformal Field Theory, Part One" - though there is no chapter called CFT Part Two. (The subject is treated further in the chapter on BRST quantization).

For CFT I, I actually opened the similarly titled chapters in Polchinski and the Becker, Becker, and Schwarz book. (I remember the CFT chapter of Kaku's book as particularly opaque). There is no doubt that the formal textbooks are far more detailed and complete, but McMahon does seem to cover some essentials.

McMahon includes some worked examples and lots of problems. The ones I looked at looked reasonably straightforward. A big question about this kind of mini-text is whether one can learn enough to work the problems, but I don't really know the answer.

The pace is undoubtedly faster than that of Zwiebach's superb elementary textbook but the prerequistes are a bit steeper - some quantum field theory and a tiny bit of differential geometry.

I think that I was impressed despite my initial reservations. This might actually be the book for that physicist wanting a birds eye view of string theory with some technical details. I might have a real review later if I get around to a full fledged read.


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