Fluid Dynamics of Systems with no Boost Invariance

When particles move in a finite density background (medium) we can imagine integrating out the medium to obtain an effective description for the motion of these particles. This will in general be a very complicated theory. However, if on large length and time scales the system is homogeneous and isotropic we can write down an effective theory for the motion of these particles in the regime where fluid dynamics applies. This requires the formulation of hydrodynamics in the absence of boost symmetries (broken by the medium) which has not been considered in generality so far. In this talk I will present the theory of homogeneous and isotropic fluid dynamics first for perfect fluids, and then generalize it to include first order transport coefficients such as viscosities and conductivities. Special attention will be given to the properties of scale invariant fluids with generic dynamical exponent z.