Covariant coarse graining of inhomogeneous dust flow in general relativity
Covariant coarse graining of inhomogeneous dust flow in general relativity
A new definition of coarse-grained quantities describing the dust flow in general relativity is proposed. It assigns the coarse-grained expansion, shear and vorticity to finite-size comoving domains of fluid in a covariant, coordinate-independent manner. The coarse-grained quantities are all quasi-local functionals, depending only on the geometry of the boundary of …