Symmetries are the result of a redundant, but useful, description of a theory.

In fact, one of the main uses of index notation is just to manifest the symmetry.

— Fields

— Warren Siegel

Siegel authored an extensive (885pg) textbook called Fields, now in its 3rd edition. It is notable in that it follows a very modern approach and incorporates many topics (including string theory) not found in other field theory textbooks. He advocates a “symmetry-based” approach and uses this in his Quantum Field Theory I&II classes. The textbook is also notable in that it is completely an “electronic book” and can be downloaded for free from Siegel’s website.

— Wikipedia on Warren Siegel

2012.02.05 Sunday ACHK