Method of moments for a relativistic single-component gas

We derive the equations of motion for all the irreducible moments of the single-particle distribution function. We find that these moment equations of motion are highly coupled, with the dynamics of lower-rank moments always being coupled to those of a higher-rank, leading to an endless tower of equations. Considering a massless gas in Bjorken flow, we investigate how this hierarchy of differential equations can be properly truncated and solved.