Gravitational radiations of generic isolated horizons and non-rotating dynamical horizons from asymptotic expansions

Instead of using a three dimensional analysis on quasi-local horizons, we adopt a four dimensional asymptotic expansion analysis to study the next order contributions from the nonlinearity of general relativity. From the similarity between null infinity and horizons, the proper reference frames are chosen from the compatible constant spinors for an observer to measure the energy-momentum and flux near quasi-local horizons. In particular, we focus on the similarity of Bondi-Sachs gravitational radiation for the quasi-local horizons and compare our results to Ashtekar-Kirshnan flux formular. The quasi-local energy momentum and flux of generic isolated horizons and non-rotating dynamical horizons are discussed in this paper.Comment: PRD, 15 page

In situ lateral earth pressure and its effect on vertical hydraulic conductivity in a glacial till deposit

The problem of permeability and preferential direction of groundwater flow in fractured glacial till has increasingly attracted the attention of researchers, particularly with regard to the possible contribution of fractures to contamination of groundwater;This research consists of a field and a laboratory phase. In the field tests, stepped blade tests (SBT) were conducted at several depths and boring locations in a glacial till deposit containing vertical and sub-vertical fractures to determine if there was any directional anisotropic nature of lateral stresses attributable to glacial flow and the formation of the fractures;The laboratory tests included soil classification and triaxial confining permeability test. Soil classification was to verify the character of till deposit at the test site. The triaxial confining test, in which a modified triaxial cell was used, was to study the effect of lateral stresses on vertical permeability of the intact and split soil samples;Soil classification indicates that the soils at the test site through the boring depth can be classified as a basal till deposit which matches the properties of the Alden Member of the Dows Formation of Des Moines Lobe;The results of SBTs indicate that the lateral stress distribution at the test site is isotropic and independent of the direction of the glacial till flow or topographic location. The isotropic lateral stress distribution implies that the vertical and sub-vertical fractures are caused by desiccation and other weathering processes rather than shear stresses induced by glacial action;The permeability tests on intact samples show that the in-situ lateral stress has a significant influence on the measurement of hydraulic conductivity. The results of the test on split samples indicate that the artificial fractures may be closed under a certain confining stress. The results of the permeability tests suggest that controlling the confining stresses in the test is important

Domain wall space-times with a cosmological constant

We solve vacuum Einstein's field equations with the cosmological constant in space-times admitting 3-parameter group of isometries with 2-dimensional space-like orbits. The general exact solutions, which are represented in the advanced and retarded null coordinates, have two arbitrary functions due to the freedom of choosing null coordinates. In the thin-wall approximation, the Israel's junction conditions yield one constraint equation on these two functions in spherical, planar, and hyperbolic domain wall space-times with reflection symmetry. The remain freedom of choosing coordinates are completely fixed by requiring that when surface energy density $\sigma_0$ of domain walls vanishes, the metric solutions will return to some well-known solutions. It leads us to find a planar domain wall solution, which is conformally flat, in the de Sitter universe.Comment: 9 pages. no figur