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conformal-transformation
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Conformally rescaled spacetimes and Hawking radiation
, Article General Relativity and Gravitation ; 2013 , Pages 1-24 ; 00017701 (ISSN) ; Firouzjaee, J. T ; Sharif University of Technology
2013
Abstract
We study various derivations of Hawking radiation in conformally rescaled metrics. We focus on two important properties, the location of the horizon under a conformal transformation and its associated temperature. We find that the production of Hawking radiation cannot be associated in all cases to a trapping horizon because its location is not invariant under a conformal transformation. We also find evidence that the temperature of the Hawking radiation should transform simply under a conformal transformation, being invariant for asymptotic observers in the limit that the conformal transformation factor is unity at their location
Cosmological Solutions of Enistien’s Equations with Axial Symmetry
, M.Sc. Thesis Sharif University of Technology ; Mansouri, Reza (Supervisor)
Abstract
In the most cosmological models which already have putted forth, metric has a spherical symmetry; however, according to the galaxy’s shape is not a real approximation. In order to build a more acqurate model, by applying a particular conformal transformation on the static vacuum solution, we introduce a new metric which is axially symmetric and also it approaches to FLRW metric at space infinity. The cosmological model according to this metric has especial features;The solution we have found represent a spacetime which is axially symmetric although it leads to a spherically symmetric Einstein tensor. Therefore, we have found a solution of Einstein equations representing a spherically...
Deriving relativistic Bohmian quantum potential using variational method and conformal transformations
, Article Pramana - Journal of Physics ; Volume 86, Issue 4 , 2016 , Pages 747-761 ; 03044289 (ISSN) ; Golshani, M ; Sarbishei, M ; Sharif University of Technology
Abstract
In this paper we shall argue that conformal transformations give some new aspects to a metric and changes the physics that arises from the classical metric. It is equivalent to adding a new potential to relativistic Hamilton-Jacobi equation. We start by using conformal transformations on a metric and obtain modified geodesics. Then, we try to show that extra terms in the modified geodesics are indications of a background force. We obtain this potential by using variational method. Then, we see that this background potential is the same as the Bohmian non-local quantum potential. This approach gives a method stronger than Bohm's original method in deriving Bohmian quantum potential. We do not...
Analysis and simulation of ring resonator silicon electro-optic modulators based on PN junction in reverse bias
, Article Optical Engineering ; Vol. 53, issue. 12 , 2014 ; ISSN: 00913286 ; Akbari, M ; Sharif University of Technology
Abstract
The theory of silicon optical modulators of ring resonators based on PN diode in reverse bias is primarily discussed. It secondarily provides a full-featured simulator to investigate the behavior of such modulators. Wave equation for ring structure will be solved by using the conformal transformation method and the matrix method as it was used to analyze bent planar optical waveguides. Power coupling between ring and straight waveguides will be calculated by coupled theory of nonparallel waveguides based on experimental results. The time response demonstrates the capability of this device to operate correctly at up to 10 Gbs-1 bitrate, and the frequency spectrum analysis of device shows a >...