A technical explanation of how the map is generated can be found at: http://blog.paperscape.org/?page_id=2 . And here are two introductory blog posts by Sean Carroll and Physics World: http://www.preposterousuniverse.com/blog/2013/08/17/a-map-of... , http://blog.physicsworld.com/2013/08/16/welcome-to-the-arxiv...