regularity;
vacuum boundary;
two-dimensional Riemann problem;
characteristic decomposition;
gas dynamics;
shock waves;
enter equations;
Goursat problem;
D O I:
10.1016/j.jde.2007.01.024
中图分类号:
O1 [数学];
学科分类号:
0701 ;
070101 ;
摘要:
We study the domain of existence of a solution to a Riemann problem for the pressure gradient equation in two space dimensions. The Riemann problem is the expansion of a quadrant of gas of constant state into the other three vacuum quadrants. The global existence of a smooth solution was established in Dai and Zhang [Z. Dai, T. Zhang, Existence of a global smooth solution for a degenerate Goursat problem of gas dynamics, Arch. Ration. Mech. Anal. 155 (2000) 277-298] up to the free boundary of vacuum. We prove that the vacuum boundary is the coordinate axes. (C) 2007 Elsevier Inc. All rights reserved.