Phenomenological and statistical analysis of fracture in polycrystalline aluminum oxide

Phenomenological and statistical analysis of fracture in polycrystalline aluminum oxid

Moduli-Space Approximation for BPS Brane-Worlds

We develop the moduli-space approximation for the low energy regime of BPS-branes with a bulk scalar field to obtain an effective four-dimensional action describing the system. An arbitrary BPS potential is used and account is taken of the presence of matter in the branes and small supersymmetry breaking terms. The resulting effective theory is a bi-scalar tensor theory of gravity. In this theory, the scalar degrees of freedom can be stabilized naturally without the introduction of additional mechanisms other than the appropriate BPS potential. We place observational constraints on the shape of the potential and the global configuration of branes.Comment: 10 pages, 1 figur

Cosmic String Wakes in Scalar-Tensor Gravities

The formation and evolution of cosmic string wakes in the framework of a scalar-tensor gravity are investigated in this work. We consider a simple model in which cold dark matter flows past an ordinary string and we treat this motion in the Zel'dovich approximation. We make a comaprison between our results and previous results obtained in the context of General Relativity. We propose a mechanism in which the contribution of the scalar field to the evolution of the wakes may lead to a cosmological observation.Comment: Replaced version to be published in the Classical and Quantum Gravit

Low Energy Branes, Effective Theory and Cosmology

The low energy regime of cosmological BPS-brane configurations with a bulk scalar field is studied. We construct a systematic method to obtain five-dimensional solutions to the full system of equations governing the geometry and dynamics of the bulk. This is done for an arbitrary bulk scalar field potential and taking into account the presence of matter on the branes. The method, valid in the low energy regime, is a linear expansion of the system about the static vacuum solution. Additionally, we develop a four-dimensional effective theory describing the evolution of the system. At the lowest order in the expansion, the effective theory is a bi-scalar tensor theory of gravity. One of the main features of this theory is that the scalar fields can be stabilized naturally without the introduction of additional mechanisms, allowing satisfactory agreement between the model and current observational constraints. The special case of the Randall-Sundrum model is discussed.Comment: 19 pages, 4 figure

Vacuum Polarization in the Spacetime of a Scalar-Tensor Cosmic String

We study the vacuum polarization effect in the spacetime generated by a magnetic flux cosmic string in the framework of a scalar-tensor gravity. The vacuum expectation values of the energy-momentum tensor of a conformally coupled scalar field are calculated. The dilaton's contribution to the vacuum polarization effect is shown explicitly.Comment: 11 pages, LATEX file, 2 eps figure

Report of the panel on earth rotation and reference frames, section 7

Objectives and requirements for Earth rotation and reference frame studies in the 1990s are discussed. The objectives are to observe and understand interactions of air and water with the rotational dynamics of the Earth, the effects of the Earth's crust and mantle on the dynamics and excitation of Earth rotation variations over time scales of hours to centuries, and the effects of the Earth's core on the rotational dynamics and the excitation of Earth rotation variations over time scales of a year or longer. Another objective is to establish, refine and maintain terrestrial and celestrial reference frames. Requirements include improvements in observations and analysis, improvements in celestial and terrestrial reference frames and reference frame connections, and improved observations of crustal motion and mass redistribution on the Earth

The Laser Astrometric Test of Relativity Mission

This paper discusses new fundamental physics experiment to test relativistic gravity at the accuracy better than the effects of the 2nd order in the gravitational field strength. The Laser Astrometric Test Of Relativity (LATOR) mission uses laser interferometry between two micro-spacecraft whose lines of sight pass close by the Sun to accurately measure deflection of light in the solar gravity. The key element of the experimental design is a redundant geometry optical truss provided by a long-baseline (100 m) multi-channel stellar optical interferometer placed on the International Space Station. The geometric redundancy enables LATOR to measure the departure from Euclidean geometry caused by the solar gravity field to a very high accuracy. LATOR will not only improve the value of the parameterized post-Newtonian (PPN) parameter gamma to unprecedented levels of accuracy of 1 part in 1e8, it will also reach ability to measure effects of the next post-Newtonian order (1/c^4) of light deflection resulting from gravity's intrinsic non-linearity. The solar quadrupole moment parameter, J2, will be measured with high precision, as well as a variety of other relativistic. LATOR will lead to very robust advances in the tests of fundamental physics: this mission could discover a violation or extension of general relativity, or reveal the presence of an additional long range interaction in the physical law. There are no analogs to the LATOR experiment; it is unique and is a natural culmination of solar system gravity experiments.Comment: 8 pages, 2 figures, invited talk given at the Second International Conference on Particle and Fundamental Physics in Space (SpacePart'03), 10-12 December 2003, Washington, D

Reconstruction of a scalar-tensor theory of gravity in an accelerating universe

The present acceleration of the Universe strongly indicated by recent observational data can be modeled in the scope of a scalar-tensor theory of gravity. We show that it is possible to determine the structure of this theory (the scalar field potential and the functional form of the scalar-gravity coupling) along with the present density of dustlike matter from the following two observable cosmological functions: the luminosity distance and the linear density perturbation in the dustlike matter component as functions of redshift. Explicit results are presented in the first order in the small inverse Brans-Dicke parameter 1/omega.Comment: 4 pages, LaTeX 2.09, REVTeX 3.0, two-column forma