We prove new estimates for the volume of a Lorentzian manifold and show especially that cosmological spacetimes with crushing singularities have finite volume. 0. Introduction Let N be a (n + 1)-dimensional Lorentzian manifold and suppose that N can be decomposed in the form (0.1) N = N0 ∪N− ∪N+, where N0 has finite volume and N− resp. N+ represent the critical past resp. future Cauchy developm...

We study uniqueness of the recovery a time-dependent magnetic vector-valued potential and an electric scalar-valued on Riemannian manifold from knowledge Dirichlet to Neumann map hyperbolic equation. The Cauchy data is observed time-like parts space-time boundary proved up natural gauge for problem. proof based Gaussian beams inversion light ray transform Lorentzian manifolds under assumptions ...

The main result of this paper is that the space of conformally compact Einstein metrics on any given manifold is a smooth, infinite dimensional Banach manifold, provided it is non-empty, generalizing earlier work of Graham-Lee and Biquard. We also prove full boundary regularity for such metrics in dimension 4 and a local existence and uniqueness theorem for such metrics with prescribed metric a...

We discuss the (2,2)-formalism of general relativity based on the (2,2)-fibration of a generic 4-dimensional spacetime of the Lorentzian signature. In this formalism general relativity is describable as a Yang-Mills gauge theory defined on the (1+1)-dimensional base manifold, whose local gauge symmetry is the group of the diffeomorphisms of the 2-dimensional fibre manifold. After presenting the...

LetM be an (n+1)-dimensional manifold with non-empty boundary, satisfying π1(M,∂M) = 0. The main result of this paper is that the space of conformally compact Einstein metrics on M is a smooth, infinite dimensional Banach manifold, provided it is non-empty. We also prove full boundary regularity for such metrics in dimension 4 and a local existence and uniqueness theorem for such metrics with p...

positive function. In such a case, we write N = N0 ×β R. In this paper we consider the case where N0 is compact. We may assume, by Nash-Moser theorem, N0 is a submanifold of R for some k > 1. By the compactness of N0, there exist constants βmin, βmax > 0 such that βmin ≤ β(x) ≤ βmax for all x ∈ N0. Let M be a Riemannian manifold with non-empty boundary ∂M . For a map w = (u, t) : M → N0 ×β R, w...

Let (M, g) be a spacetime, where M is a smooth, connected, Hausdorff four-dimensional manifold and g is smooth Lorentzian metric of signature (+ -) defined on M . The manifold M and the metric g are assumed smooth (C). A smooth vector field ξ is said to preserve a matter symmetry [1] on M if, for each smooth local diffeomorphism φt associated with ξ, the tensors T and φ∗tT are equal on the doma...

The main result of this paper is that a Lorentzian manifold is locally conformally equivalent to a manifold with recurrent lightlike vector field and totally isotropic Ricci tensor if and only if its conformal tractor holonomy admits a 2-dimensional totally isotropic invariant subspace. Furthermore, for semi-Riemannian manifolds of arbitrary signature we prove that the conformal holonomy algebr...

It is argued that the problems of the cosmological constant, stability and renormalizability of quantum gravity can be solved if the space-time manifold is not fundamental, but arises through spontaneous symmetry breaking. A “pre-manifold” model is presented in which many points are connected by random bonds. A set of D real numbers is assigned to each point. These numbers are coupled between p...

We present a systematic study of causality theory on Lorentzian manifolds with continuous metrics. Examples are given which show that some standard facts in smooth Lorentzian geometry, such as light-cones being hypersurfaces, are wrong when metrics which are merely continuous are considered. We show that existence of time functions remains true on domains of dependence with continuous metrics, ...