  I review what is required to compute transport coefficients in
ultra-relativistic, weakly coupled gauge theories, at leading order in $g$,
using kinetic theory. Then I discuss how the calculation would look in
alternative approaches: the 2PI method, and direct diagrammatic analysis. I
argue that the 2PI method may be a good way to derive the kinetic theory, but
is not very useful directly (in a gauge theory). The diagrammatic approach is
almost hopeless.

High Energy Physics - Phenomenology