Relativistic Bulk Viscosity In The Relaxation Time Approximation: A Chaotic Velocities Approach

In this short note, the bulk viscosity for a high temperature dilute gas is calculated by applying the Chapman-Enskog method within Marle's relaxation time approximation. The expression for the stress-tensor established in Ref. [1], using explicitly the concept of chaotic velocity, is used in order to obtain the transport coefficient. The result is compared with previous expressions obtained by other authors using similar methods and emphasis is made on the agreement when a corrected relaxation parameter is considered.