10 research outputs found
The Constraints in Spherically Symmetric General Relativity II --- Identifying the Configuration Space: A Moment of Time Symmetry
We continue our investigation of the configuration space of general
relativity begun in I (gr-qc/9411009). Here we examine the Hamiltonian
constraint when the spatial geometry is momentarily static (MS). We show that
MS configurations satisfy both the positive quasi-local mass (QLM) theorem and
its converse. We derive an analytical expression for the spatial metric in the
neighborhood of a generic singularity. The corresponding curvature singularity
shows up in the traceless component of the Ricci tensor. We show that if the
energy density of matter is monotonically decreasing, the geometry cannot be
singular. A supermetric on the configuration space which distinguishes between
singular geometries and non-singular ones is constructed explicitly. Global
necessary and sufficient criteria for the formation of trapped surfaces and
singularities are framed in terms of inequalities which relate appropriate
measures of the material energy content on a given support to a measure of its
volume. The strength of these inequalities is gauged by exploiting the exactly
solvable piece-wise constant density star as a template.Comment: 50 pages, Plain Tex, 1 figure available from the authors
Geometric Bounds in Spherically Symmetric General Relativity
We exploit an arbitrary extrinsic time foliation of spacetime to solve the constraints in spherically symmetric general relativity. Among such foliations there is a one parameter family, linear and homogeneous in the extrinsic curvature, which permit the momentum constraint to be solved exactly. This family includes, as special cases, the extrinsic time gauges that have been exploited in the past. These foliations have the property that the extrinsic curvature is spacelike with respect to the the spherically symmetric superspace metric. What is remarkable is that the linearity can be relaxed at no essential extra cost which permits us to isolate a large non - pathological dense subset of all extrinsic time foliations. We identify properties of solutions which are independent of the particular foliation within this subset. When the geometry is regular, we can place spatially invariant numerical bounds on the values of both the spatial and the temporal gradients of the scalar areal radiu..
Sufficient Conditions for Apparent Horizons in Spherically Symmetric Initial Data
We establish sufficient conditions for the appearance of both apparent horizons and singularities in spherically symmetric initial data when spacetime is foliated extrinsically. Let M and P be respectively the total material energy and the total material current contained in some ball of radius `. Suppose that the dominant energy condition is satisfied. We show that if M \Gamma P ` then the region must possess a future apparent horizon for some non-trivial closed subset of such gauges. The same inequality holds on a larger subset of gauges but with a larger constant of proportionality which depends weakly on the gauge. This work extends substantially both our joint work on moment of time symmetry initial data as well as the work of Bizon, Malec and ' O Murchadha on a maximal slice. Typeset using REVT E X [email protected] y [email protected] I. INTRODUCTION This paper is part of an ongoing examination of the constraints in spherically symmetric general relativity [1--3]. Here we..
Necessary Conditions for Apparent Horizons and Singularities in Spherically Symmetric Initial Data
We establish necessary conditions for the appearance of both apparent horizons and singularities in the initial data of spherically symmetric general relativity when spacetime is foliated extrinsically. When the dominant energy condition is satisfied these conditions assume a particularly simple form. Let ae Max be the maximum value of the energy density and ` the radial measure of its support. If ae Max ` 2 is bounded from above by some numerical constant, the initial data cannot possess an apparent horizon. This constant does not depend sensitively on the gauge. An analogous inequality is obtained for singularities with some larger constant. The derivation exploits Poincar'e type inequalities to bound integrals over certain spatial scalars. A novel approach to the construction of analogous necessary conditions for general initial data is suggested. Typeset using REVT E X [email protected] y [email protected] I. INTRODUCTION In this paper we cast necessary conditions for the a..