11·î29Æü(ÌÚ) 15:30 -- 17:00 Prof. Tai-Ping Liu (Ãæ±û¸¦µæ±¡¡¢ÂæÏÑ) ``Gas Flows with Vacuum'' ¡ã¸¦µæȯɽÍ׻ݡä We will consider inviscid gas flows with vacuum. There are two problems: The first is Euler equations with damping for the study of porous media flows. The second are Euler-Poisson equations for the study of gaseious stars. In both cases, the systems is not symmetrizable at vacuum. There are also the questions of waiting time, stability and instability. For instance, the threshold of stability for the gaseous stars is the adiabetic exponent equal to 4/3, and there are more than one version of stability. We will survey these issues and indicate the analytical ideas for their study.