dc.contributor.author Elmardi, Maye dc.date.accessioned 2018-11-16T06:48:43Z dc.date.available 2018-11-16T06:48:43Z dc.date.issued 2018 dc.identifier.citation Elmardi, E. 2018. The cosmological perturbed lightcone gauge. Universe, 4(10): Article no 108. [https://doi.org/10.3390/universe4100108] en_US dc.identifier.issn 2218-1997 (Online) dc.identifier.uri http://hdl.handle.net/10394/31718 dc.identifier.uri https://doi.org/10.3390/universe4100108 dc.identifier.uri https://www.mdpi.com/2218-1997/4/10/108/pdf dc.description.abstract The lightcone gauge is a set of what are called the observational coordinates adapted to our past lightcone. We develop this gauge by producing a perturbed spacetime metric that describes the geometry of our past lightcone where observations are usually obtained. We connect the produced observational metric to the perturbed Friedmann-Lemaître-Robertson-Walker (FLRW) metric in the standard general gauge or what is the so-called 1+3 gauge. We derive the relations between these perturbations of spacetime in the observational coordinates and those perturbations in the standard metric approach, as well as the dynamical equations for the perturbations in observational coordinates. We also calculate the observables in the lightcone gauge and re-derive them in terms of Bardeen potentials to first order. A verification is made of the observables in the perturbed lightcone gauge with those in the standard gauge. The advantage of the method developed is that the observable relations are simpler than in the standard formalism, and they are expressed in terms of the metric components which in principle are measurable. We use the perturbed lightcone gauge in galaxy surveys and the calculations of galaxy number density contrast. The significance of the new gauge is that by considering the null-like light propagations the calculations are much simpler due to the non-consideration of the angular deviations en_US dc.language.iso en en_US dc.publisher MDPI en_US dc.subject General relativity en_US dc.subject Past lightcone gauge en_US dc.subject Direct observational approach en_US dc.subject Cosmological observables en_US dc.subject Galaxy surveys en_US dc.subject Galaxy number count en_US dc.subject Density contrast en_US dc.subject Overdensity en_US dc.subject Cosmological perturbations en_US dc.title The cosmological perturbed lightcone gauge en_US dc.type Article en_US dc.contributor.researchID 28923510 - Elmardi, Maye
﻿

Theme by