# string theory books

some opinions & comments

## Public scientific books:

Over the past decades quite a number of popular scientific / non-expert books on string theory and related subjects were published, following the great success of Hawking’s legendary “A Brief History of Time”. Personally, I still regard Brian Greene’s “The Elegant Universe” as one of the best (if not *the* best) books on string theory, despite the fact that it is by now more than a decade old and therefore does not discuss the most recent developments.

In the following list I collect a number of popular-scientific books you may want to take a closer look at:

Greene’s “The Elegant Universe”, which was released in 1999, gives a very readable and lengthy popular-scientific introduction to the general subject of quantum gravity and then delves deeper into string theory. The book was an enourmous success, and was later recompiled into a three-hour TV mini-series, which is available on YouTube in split videos. However, the TV-show neglects many interesting aspects, which are only found in the book. This was one of the few books, that stirred me into the direction of string theory. One should note that the book’s successor “The Fabric of the Cosmos” (published in 2005) is of considerable lower quality in my opinion. It seems to be a light version of his first book, which I cannot recommend to anyone who has read the “The Elegant Universe”. On the other hand, if “The Elegant Universe” seems a little bit too complex or dense to your liking, the book may still have some value. Furthermore, it is a little bit more up to date concerning modern developments. |

In his 2001 book “Three Roads to Quantum Gravity” Smolin reviews three different approaches that address the issue of quantum gravity and the unification of all four known interactions. Aside from string theory and M-theory (which he discusses seperate from string theory), a considerable part of the book is spend on Loop Quantum Gravity and the holographic principle. The book provides a rather broad overview on the subject and considering its size can be an interesting read even. Published in 2001, the book is not up to the most recent developments. It should be noted that Smolin broke up with string community with the publication of his highly controversal 2006 book “The Trouble With Physics”, where he raises general questions regarding modern scientific methods and puts the entire development of string theory into question. |

The quite massive book “The Road to Reality: A Complete Guide to the Laws of the Universe” was written by the British physicist and mathematician Roger Penrose and published in 2004. It is rather unique, as it builds up most of physics from the ground up, but at a level considerable higher than most popular-scientific books, yet still extremely accessible. This is mainly due to the fact that he does not try to avoid the usage of formulas like almost every other author. In the later chapters, Penrose gives concise reviews of string theory, loop quantum gravity and twistor theory, a formalism invented by himself author in the 70s. Even to an expert, the fresh perspective he provides on many well-known and established facts makes the read very worth-wile, however, completing the 1000-page doorstopper takes some time. |

Lisa Randall “Warped Passages” was released in 2005, and proved to be the first major successful popular-scientific book by a female physicist. It focusses on the extra dimensions implied by the string theory, the Kaluza-Klein mechanism and compactification. Despite all the positive reviews and critical acclaim I did not find anything really outstanding in the book. It rather recollects many old and well-known facts on compact dimensions and how one may try to understand them. Naturally, she explains her co-developed Randall-Sundrum model as an alternative to compactification in great detail. Nevertheless, in my humble opinion, there are far better non-expert string theory books out there… |

…like for example this one! In “The Cosmic Landscape: String Theory and the Illusion of Intelligent Design” the well-known physicist Leonard Susskind sheds a light on the string theory landscape and many of its not-so-well-known implications. He discusses the relevance of the anthropic principle and explains the potential grounds on which one can think of the landscape in terms of describing a multiverse instead of a single isolated universe vacuum. This 2005 book certainly requires some deeper thinking and is not as accessible as most of the others listed here, but if you have some background it is by far the most rewarding. A little bit on the side-line, in 2008 Susskind also published “The Black Hole” war, where he discusses the legendary inner-physics war between himself and Stephen Hawking regarding the information loss paradoxon in black holes. While the book only briefly mentions string theory and the stringy description of black holes, it is a very nice book on modern and elementary particle physics, which discusses the very fundamentals upon which our understanding of the world is based. |

A few years ago I got the book “Out of This World: Colliding Universes, Branes, Strings, and Other Wild Ideas of Modern Physics” from a friend. Written in 2004 by Stephen Webb, I was extremely surprised by the overall quality of the exposition. A really nice aspect of the book is its actual introduction of known physics. Where most other authors of popular scientific book rather quickly skim throught the known material (e.g. the Standard Model) in order to arrive at their respective main topic. Not the case here: More than half of the book covers known and well-established physics, which really highlights the actual problems and questions that need to be investigated. After that GUTs and supersymmetry are introduced, with string theory and relatic topics taking up the rest of the book. Highly recommended. |

One should keep in mind, that most book reviews are extremely biased—and I am by no means a book critic. Futhermore, with regard to the specific subject at hand, one should never forget a readers background. Evaluating popular-scientific texts from an expert’s perspective is always difficult, since everything seems to be absolutely clear and written for plain understanding. However, actually mastering most of those concepts on first read may (have been) much more difficult as the one may admit. So **don’t take my recommendations too seriously…**

## Expert books:

Once you decide to really delve deeper into the subject of string theory, there is no real alternative to the established reference works published over the last decades. Some of the books are pretty old and are quite out-dated with respect to more modern developments, but still there is lots of valuable information in them.

The enigmatic and legendary book “Superstring theory” and volume 2 by Green, Schwarz and Witten dates back to 1987/88, so both volumes are rather old and outdated. Nevertheless, it is still considered to be one of the primary sources of information if you want to take a deeper look into anomaly cancellation and loop amplitude computations in string theory. Certainly it misses the developments of the past two decades and may appear cumbersome in some aspects of the presentation from a modern perspective, but one should still have it at an arms length in case needed. It also gives a rather detailed introduction (for a theoretical physics book) into the mathematics of algebraic geometry and Calabi-Yau geometries. |

Polchinski’s book “String Theory” and volume 2 is the second “big” standard work on string theory and dates back to 1998, so it covers two big discoveries of the 90s: D-branes, which were found by the author himself, and some elementary facts of M-theory theory and other non-perturbative aspects of string theory. The book has a strong technical focus on vertex operators and the relevant conformal field theory and is certainly intended for readers with some serious background in quantum field theory. The overall presentation of the material is rather dense, but the book serves as a very good reference on details which appear in the course of one’s own study and reserarch. |

Published in late 2006, the volume “String Theory and M-Theory” by K. Becker, M. Becker and Schwarz is a pretty recent one and covers a wide range of materials. However, the wide range of the covered material makes the book a little bit superficial in many aspects, as no subject is really covered in detail. Many computations are omitted and left to the reader, which does not make it a handy reference. The book rather seems to serve to those, who are still looking for a topic to investigate further. As a bonus point it is the only text book that covers black holes and flux compactifications, but the M-theory part mentioned in the title is rather short. Furthermore, the AdS/CFT correspondence, one of the big developments of the late ’90s is only covered in brief terms. |

Kiritsis’s “String Theory in a Nutshell” is perhaps the most useful textbook of the hole collection. It is pretty modern (gone public in 2007) and follows a very straight path, where most of the computations are more or less straightforward and reasonable. The book seems to be the ideal reference for the desk, as I find myself often skimming through the pages when in doubt about some specific aspect. Contrary to the aforementioned book, it only skims M-theory, but spends a good deal of space on the AdS/CFT correspondence. Overall, this book is a must have for every working string theorist. |

The little hardcover book “Introduction to String Theory and D-Brane Dynamics” by Szabo from 2004 does not seem like much when one holds it in his hands. It starts at a very elementary level and develops the basics of string theory from the ground up. After that D-branes are introduced, followed by a very nice derivation of the Chern-Simons action term, which I found pretty useful back at the time of reading. Certainly not a must-have, but a nice addition to any collection. |

The big green one called “D-Branes” on your desk was written by Clifford Johnson and covers almost every aspect remotely connected to the subject of D-branes. It starts with a rather concise summary and introduction to string theory, but quickly builds momentum in the direction of BPS states and D-branes. From there, many details are covered, in particular the geometrical and non-perturbative aspects concerning those higher-dimensional ingredients of string theory. As a nice aspect, it covers M- and F-theory from the brane perspective and the effects of the various dualities. Overall this 2003 book is a very handy reference on all things D-brane, and an early development stage of the book is freely available here. |

When taking a first look at Barton Zwiebach’s book “A First Course in String Theory” in 2004 I was at first a little bit stumped at the apparent lack of any higher developments, like for example the “super” in superstrings. However, shortly after I realized that his actual intention was to make the underlying basics of string theory accessible to undergraduates, which was in fact masterfully done. The text developes string theory from most elementary results of quantum mechanics and does it all in vast detail not found in any other textbook. Anyone with a certain grasp on quantum mechanics and a little bit of special relativity as well as quantum field theory should be able to work through the text. It even introduces the concepts of compactification and the T-duality. Obviously, the book does not go anywhere near the more involved topics, but it certaily provides a very firm basis for further investigation. |

I more or less bought the 2008 book “String Theory: Demystified” just to have another string theory text at home. While I have not yet read the entire book, the sections I did take a closer look at seemed pretty understandable. However, the book is lacking all the deeper insight you may find in the more seasoned reference works. If one is truly inclined to work through the book, a certain level of technical understanding is reached but almost certainly no deeper or “real” understanding. Considering the size and overall markup of the so-called self-teaching guide, this was probably not the onset of the author David McMahon. Overall, it is a decent book, but no certainly no master-piece or reference work. |

Once again, I would like to point out the **biased perspective of the above recommendations**. Everyone favors a different kind of text book, e.g. more example driven or with detailed computations of all shown results. I usually tend to value “deep insights” much higher than pages full of computations, but ultimately one certainly has to do the laborous work…