title: No regularity singularities exist at points of general relativistic shock wave interaction between shocks from different characteristic families.
abstract: We give a constructive proof that coordinate transformations exist which raise the regularity of the gravitational metric tensor fromC0,1toC1,1in a neighbourhood of points of shock wave collision in general relativity. The proof applies to collisions between shock waves coming from different characteristic families, in spherically symmetric spacetimes. Our result here implies that spacetime is locally inertial and corrects an error in our earlierProc. R. Soc. Apublication, which led us to the false conclusion that such coordinate transformations, which smooth the metric toC1,1, cannot exist. Thus, our result implies that regularity singularities (a type of mild singularity introduced in ourProc. R. Soc. Apaper) donot existat points of interacting shock waves from different families in spherically symmetric spacetimes. Our result generalizes Israel's celebrated 1966 paper to the case of such shock wave interactions but our proof strategy differs fundamentally from that used by Israel and is an extension of the strategy outlined in our originalProc. R. Soc. Apublication. Whether regularity singularities exist in more complicated shock wave solutions of the Einstein-Euler equations remains open.
authors.affiliation: IMPA-Instituto Nacional de Matemática Pura e Aplicada , Rio de Janeiro, Brazil.
authors.forename: Moritz
authors.initials: M
authors.lastname: Reintjes
authors.affiliation: Department of Mathematics , University of California , Davis, CA 95616, USA.
authors.forename: Blake
authors.initials: B
authors.lastname: Temple
keywords: Einstein–Euler equations; general relativity; hyperbolic conservation laws; regularity singularity; shock wave interactions