CMSA General Relativity: Rough solutions of the relativistic Euler equations

 I will discuss recent works on the relativistic Euler equations with dynamic vorticity and entropy. We use a new formulation of the equations, which has geo-analytic structures. In this geometric formulation, we decompose the flow into geometric "sound-wave part" and "transport-div-curl part". This allows us to derive sharp results about the dynamics, including the existence of low-regularity solutions. Then, I will discuss the results of rough solutions of the relativistic Euler equations and the role that nonlinear geometric optics plays in the framework, . Our main result is that the Sobolev norm $H^{2+}$ of the variables in the ``wave-part" and the H\"older norm $C^{0,0+}$ of the variables in the ``transport-part" can be controlled in terms of initial data for short times. We note that the Sobolev norm assumption $H^{2+}$ is the optimal result for the variables in the ``wave-part." This talk will include the main ideas of the proof, as well as a comparison of the relativistic and non-relativistic scenarios.