4 Resources 

• A valuable resource for finding relevant literature is the comprehensive ``Bibliography of Publications Related to Classical and Quantum Gravity in terms of Connection and Loop Variables'', organized chronologically. The original version was compiled by Peter Hübner in 1989. It has subsequently been updated by Gabriella Gonzales, Bernd Brügmann, Monica Pierri and Troy Shiling. Presently, it is being kept updated by Christopher Beetle and Alejandro Corichi. The latest version can be found on the net in [44].
• This ``living review'' may serve as an up to date introduction to quantum gravity in the loop formalism. More detailed (but less up to date) presentations are listed below.
  • Ashtekar's book [9] may serve as a valuable basic introductory course on Ashtekar variables, particularly for relativists and mathematicians. The part of the book on the loop representation is essentially an authorized reprint of parts of the original Rovelli Smolin article [184]. For this quantum part, I recommend looking at the article, rather than the book, because the article is more complete.
  • A simpler and more straightforward introduction to the Ashtekar variables and basic loop ideas can be found in the Rovelli's review paper [164]. This is more oriented to a reader with a physics background.
  • A recent general introduction to the new variables which includes several of the recent mathematical developments in the quantum theory is given by Ashtekar's Les Houches 1992 lectures [10].
  • A particularly interesting collection of papers can be found in the volume [29] edited by John Baez . The other book by Baez, and Muniain [36], is a simple and pleasant introduction to several ideas and techniques in the field.
  • The last and up to date book on the loop representation is the book by Gambini and Pullin [93], especially good in lattice techniques and in the variant of loop quantum gravity called the ``extended loop representation'' [80, 78] (which is nowadays a bit out of fashion, but remains an intriguing alternative to ``orthodox'' loop quantum gravity).
  • The two standard references for a complete presentation of the basics of the theory are: DePietri and Rovelli [77] for the algebraic formulation ; and Ashtekar, Lewandowski, Marolf, Mourao and Thiemann () [18] for the differential formulation .
• Besides the many conferences on gravity, the loop gravity community has met twice in Warsaw, in the ``Workshop on Canonical and Quantum Gravity'' . Hopefully, this will become a recurrent meeting. This may be the right place to go for learning what is going on in the field. For an informal account of the last of these meetings (August 1997), see [161].
• Some of the main institutions where loop quantum gravity is studied are
  • The ``Center for Gravity and Geometry'' at Penn State University, USA. I recommend their invaluable web page [157], maintained by Jorge Pullin, for finding anything you need from the web.
  • Pittsburgh University, USA [100].
  • University of California at Riverside, USA. John Baez moderates an interesting newsgroup, sci.physics.research, with news from the field. See [34].
  • Albert Einstein Institute, Potsdam, Berlin, Europe [117].
  • Warsaw University, Warsaw, Europe.
  • Imperial College, London, Europe [67].
  • Syracuse University, USA [208].
  • Montevideo University, Uruguay.

Loop Quantum Gravity Carlo Rovelli http://www.livingreviews.org/lrr-1998-1 © Max-Planck-Gesellschaft. ISSN 1433-8351 Problems/Comments to livrev@aei-potsdam.mpg.de