Propagation of jump discontinuities in relativistic cosmology - art. no. 104023

A recent dynamical formulation at a derivative level partial derivative (3) g for fluid spacetime geometries (M,g,u), that employs the concept of evolu tion systems in a first-order symmetric hyperbolic format, implies the exis tence in the Weyl curvature branch of a set of timelike characteristic thre e-surfaces associated with the propagation speed \upsilon\ = 1/2 relative t o fluid-comoving observers. We show it is a physical role of the constraint equations to prevent realization of jump discontinuities in the derivative s of the related initial data so that Weyl curvature modes propagating alon g these three-surfaces cannot be activated. In addition we introduce a new, illustrative first-order symmetric hyperbolic evolution system at a deriva tive level partial derivative (2)g for baryotropic perfect fluid cosmologic al models that are invariant under the transformation of an Abelian G(2) is ometry group.