부산대학교 도서관

Summary: ``It is well known that the equations for a simple fluid can be cast into what is called their Lagrange formulation. We introduce the notion of a generalized Lagrange formulation, which is applicable to a wide variety of systems of partial differential equations. These include numerous systems of physical interest, in particular, those for various material media in general relativity. We prove a key theorem to the effect that if the original (Euler) system admits an initial-value formulation, then so does its generalized Lagrange formulation.''