String Theory (Vols 1 and 2)

"Polchinki’s book stands as a very different achievement. It’s something which he spent years writing and refining, so it’s this gorgeously edited and refined book. He also retains an impressive website where he’s caught all the errors in the equations, and corrected them. It is a work of tremendous care and detail, but it doesn’t quite have that quality of Green, Schwarz, Witten of being the instant classic. It’s more the considered classic. It includes the key early ideas of what’s known as the second superstring revolution. People had taken the notions from the Green, Schwarz, Witten textbook (and the many papers on which it was based) as far as they were going to go, and it seemed that some really new ideas were needed. Those ideas had a more geometrical flavour. They had to do with dimensions of space and time emerging from dynamics, and with new objects, other than strings, entered into the story. And that is where Polchinski made his own greatest contribution, which goes by name of the D-brane. D-branes are a big part of my own book on string theory, and they are objects like strings in that they have spatial extent; but they’re much heavier than strings. These are some of the ideas that Polchinski brought into the field, through his research papers, and he captured those ideas in his book in an elegant and very systematic way."