book reviews
## String theory booksreviewed by T. Nelson |

by Andrew Zimmerman Jones

Wiley, 2010, 364 pages

reviewed by T. Nelson

This one gives a nice, simple, conceptual overview of string theory for laymen. The first half is a nontechnical description of the background physics, teaching people basic stuff like what a boson is, what is symmetry breaking, and the standard model of particle physics. Then it teaches the concepts of string theory in such a way that anyone can understand them, with no math. It doesn't talk down to the readers, make them feel like dummies, or make goofy jokes; it just assumes you are curious as to what it's all about.

In the last part it gets a little science-fictiony, with stuff about time travel and the like; but then it gets back on track and gives a fair assessment of alternative theories such as loop quantum gravity, modified Newtonian dynamics, and so forth.

Despite the title, you can learn a lot; I know one Ph.D. molecular biologist
who has a whole shelf full of these *For Dummies* books and swears by them.
But then, he swears about quite a lot of things.

* dec 22, 2015*

by Makoto Natsuume

Springer, 2015, 294 pages

reviewed by T. Nelson

Although the title makes it sound like a computer book, this book actually describes a theory in modern physics that analyzes gauge theories as gravitational objects.

AdS/CFT duality, formerly known as Maldacena's conjecture, is an idea from superstring theory. It posits an equivalence, or duality, between gravitational theory in five-dimensional anti-de Sitter spacetime and strongly coupled four-dimensional gauge theory, also known as conformal field theory or CFT. Since the dimensionality of these two theories is different, AdS/CFT is an example of a holographic theory. But it is finding use not just in gravitational theories, but also in theories about quark-gluon plasma and even in theories about the nature of space that are still being developed.

The presentation is quite a bit higher than the book reviewed at left. It requires
a basic understanding of general relativity and quantum field theory. For the
latter, Maggiore is a perfect fit, as he starts out with Poincaré
symmetries and has a good chapter on non-abelian gauge theory (aka Yang-Mills
transformations). Another great source of background knowledge is *Particles
and Fundamental Interactions* by Braibant, Giacomelli, and Spurio, which has
a chapter on ordinary everyday gauge transformations covered in a very
understandable way.

Natsuume introduces the topic by discussing black hole thermodynamics. He shows how black hole entropy is proportional to area, while statistical entropy is proportional to volume. Thus a 5-dimensional black hole would correspond to a 4-dimensional statistical system. This statistical system, according to AdS/CFT, is a gauge theory.

The book focuses on real-world applications of AdS/CFT ranging from string theory to quark-gluon plasma, which gets its own chapter. Natsuume emphasizes conceptual understanding as well as the mathematics. This is not, strictly speaking, a string theory book, though strings and branes figure prominently.

Publishers love books on string theory because the figures are very easy to
create—just straight lines. The only problem is that some strings are
infinitely long. Other books on this topic are *Introduction
to AdS/CFT Correspondence* by Nastase and *Gauge/Gravity Duality:
Foundations and Applications* by Ammon and Erdmenger.

* dec 29, 2015; updated dec 30, 2015*