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Full-Text Articles in Physics
Deriving The Dyer-Roeder Equation From The Geodesic Deviation Equation Via The Newman-Penrose Null Tetrad, Aly Aly
Undergraduate Review
In this paper we examine the geodesic deviation equation using the Newman-Penrose (N-P) formalism for a flat Friedmann-Lemaitre-Robertson-Walker(FLRW) metric [Carroll,S. (2004), Ryden, B. (2003), Newman Penrose(1962)]. We solved the geodesic deviation equation for angular diameter distance, using the relevant N-P components, and the resulting expression was the Dyer-Roeder equation of cosmology [Ryden, B. (2003)] [Schneider et al.(1992)]. This leads us to believe that we can apply the N-P formalism to a perturbed FLRW metric and find a solvable equation for angular diameter distance [Kling Campbell(2008)]. The perturbed FLRW metric incorporates clumps of matter into a metric that is on average …
Computer Programming To Advance Gravitational Lensing, Alex Roche
Computer Programming To Advance Gravitational Lensing, Alex Roche
Undergraduate Review
The purpose of this research was to create a computer code that would numerically test a Poisson equation relating the mass distribution of a lens galaxy cluster to weak gravitational shear. Einstein’s theory of general relativity predicts that space-time is bent by massive objects, and in weak gravitational lensing, galaxy clusters act as lenses. The observable result is that galaxies far behind the gravitational lens will appear slightly more elliptical than they actually are. The ellipticity of the background galaxies is quantifiable and is directly related to the weak gravitational shear, and the shear is used to determine the mass …
An Optical Scalar Approach To Weak Gravitation Lensing, Louis Bianchini
An Optical Scalar Approach To Weak Gravitation Lensing, Louis Bianchini
Undergraduate Review
We assume a thick gravitational lens governed by a Baltz n=1 matter density model. From the gravitational potential we then derive expressions for a Weyl tensor component and Ricci tensor component. A perturbative approach is taken to solve for the convergence and shear as given by Sach’s equation. By applying the geodesic deviation equation to a bundle of light rays with our expressions for the optical scalars we are able to derive expressions for the image shape and size at any point along the path from source to observer, in the case of an axially symmetric lens and source.
Modeling Weak Gravitational Lensing Through C++, Christopher Cepero
Modeling Weak Gravitational Lensing Through C++, Christopher Cepero
Undergraduate Review
Gravitational Lensing has become an integral part of astrophysics and the study of matter in the universe. In weak gravitational lensing, an object appears distorted when viewed from the observer’s perspective. This is caused by the bundle of light being distorted by an object of considerable mass. Because the distance to each part of this bundle is not the same, the rays of light are affected differently causing a shearing and magnification of the image. This alteration in the image we see can be modeled using the thin lens approximation. By integrating the equations for light travel based on general …
Superconducting Phases In Bulk And Thin Film La2Cuo4, Brandon Green
Superconducting Phases In Bulk And Thin Film La2Cuo4, Brandon Green
Undergraduate Review
La2CuO4 is considered as the parent material of all high temperature superconductors. The magnetic nature of the material is antiferromagnetic and it is an insulator. During this research we produced a superconductor by doping ceramic La2CuO4 with excess oxygen. There are different methods to intercalate excess oxygen into a sample, but in this project we used an electrochemical method. After oxidation, the superconducting properties were measured using a Quantum Design MPMS SQUID magnetometer. The superconducting transition temperature (TC) was observed near 40 K with a superconducting volume fraction of 16%. Further oxidation …
The E.P.R. Paradox, George Levesque