User predrag cvitanović - MathOverflow most recent 30 from http://mathoverflow.net 2013-05-25T10:59:45Z http://mathoverflow.net/feeds/user/4644 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/6139/how-can-i-learn-about-doing-linear-algebra-with-trace-diagrams/18239#18239 Answer by Predrag Cvitanović for How can I learn about doing linear algebra with trace diagrams? Predrag Cvitanović 2010-03-15T03:05:12Z 2010-03-15T03:05:12Z <p>to Greg Kuperberg: Use of such diagrams probably starts in mid 19th century <a href="http://birdtracks.eu/version8.9/GroupTheory.pdf" rel="nofollow">(Sect. 4.9 A BRIEF HISTORY OF BIRDTRACKS)</a>. If you find "spiders" or “birdtracks” too silly, I vote for the somewhat unwinged "tensor diagrams." </p> <p> So why give these diagrams a new name, and not call them “Feynman diagrams” or "tensor diagrams"? I needed a distinct name to distinguish them from the more traditional uses of diagrams. The difference is that here diagrams are not a mnemonic device, an aid in writing down a Feynman integral that is to be evaluated by other techniques. I did not call them "tensor diagrams" as that is too close to “invariant tensor operators”, the Wigner-Eckart theorem, and the 3n-j diagrams that are only a prelude to a computation. Here “birdtracks” are everything, all calculations are carried out in terms of birdtracks, from start to finish. </p>