摘要：The hard phase model is an idealized model for a relativistic fluid where the sound speed approaches the speed of light. In this talk I will first review our results on the well-posedness for the free boundary problem of this model, then I will present our recent work on linear (in)stability for a family of steady states to this problem. This talk is based on joint works with Sohrab Shahshahani, Sijue Wu and Zeming Hao.