Birdtracks under the sun (course on the birdtrack technique)

The diagrammatic approach to calculating group theoretical factors is a powerful technical tool in quantum field theory. The diagrams used in these calculations are known as "birdtracks" and they complement the mainstream approaches based on Feynman diagrams. In the context of quantum chromodynamics, SU(3), birdtracks intuitively represent the color flow of the process being examined and can be easily extended to any value of N.

This series of lectures introduces elementary birdtracks and provides practice exercises. Topics of interest include constructing projection operators and invariant charges, their relationship with permutation operators and Young-diagrams, and evaluating Wilson lines correlators in the Gaussian approximation. Although the lectures primarily focus on the SU(N) group, the birdtrack approach is generic and can be applied to other groups, such as the Clifford group.

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