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dc.contributor.authorElmardi, Maye
dc.date.accessioned2018-11-16T06:48:43Z
dc.date.available2018-11-16T06:48:43Z
dc.date.issued2018
dc.identifier.citationElmardi, E. 2018. The cosmological perturbed lightcone gauge. Universe, 4(10): Article no 108. [https://doi.org/10.3390/universe4100108]en_US
dc.identifier.issn2218-1997 (Online)
dc.identifier.urihttp://hdl.handle.net/10394/31718
dc.identifier.urihttps://doi.org/10.3390/universe4100108
dc.identifier.urihttps://www.mdpi.com/2218-1997/4/10/108/pdf
dc.description.abstractThe 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 deviationsen_US
dc.language.isoenen_US
dc.publisherMDPIen_US
dc.subjectGeneral relativityen_US
dc.subjectPast lightcone gaugeen_US
dc.subjectDirect observational approachen_US
dc.subjectCosmological observablesen_US
dc.subjectGalaxy surveysen_US
dc.subjectGalaxy number counten_US
dc.subjectDensity contrasten_US
dc.subjectOverdensityen_US
dc.subjectCosmological perturbationsen_US
dc.titleThe cosmological perturbed lightcone gaugeen_US
dc.typeArticleen_US
dc.contributor.researchID28923510 - Elmardi, Maye


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