The effect of pressure gradients on luminosity distance-redshift relations

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Title: The effect of pressure gradients on luminosity distance-redshift relations
Author(s): Lasky, Paul D.; Bolejko, Krzysztof
Abstract: Inhomogeneous cosmological models have had significant success in explaining cosmological observations without the need for dark energy. Generally, these models imply that inhomogeneous matter distributions alter the observable relations that are taken for granted when assuming that the Universe evolves according to the standard Friedmann equations. Moreover, it has recently been shown that both inhomogeneous matter and pressure distributions are required in both early and late stages of cosmological evolution. These associated pressure gradients are required in the early Universe to sufficiently describe void formation, whilst late-stage pressure gradients stop the appearance of anomalous singularities. In this paper we investigate the effect of pressure gradients on cosmological observations by deriving the luminosity distance-redshift relations in spherically symmetric, inhomogeneous spacetimes endowed with a perfect fluid. By applying this to a specific example for the energy density distribution and using various equations of state, we are able to explicitly show that pressure gradients may have a non-negligible effect on cosmological observations. In particular, we show that a non-zero pressure gradient can imply significantly different residual Hubble diagrams for z less than or similar to 1 compared to that when the pressure is ignored. This paper therefore highlights the need to properly consider pressure gradients when interpreting cosmological observations.
Publication type: Journal article
Research centre: Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing
Source: Classical and Quantum Gravity, Vol. 27, no. 3 (Feb 2010), p. 13
Publication year: 2010
FOR Code(s): 0105 Mathematical Physics; 0206 Quantum Physics
Keyword(s): Cosmological models; Cosmological observations; Dark energy; Distance-redshift relations; Pressure gradients
Publisher: IOP Publishing
ISSN: 0264-9381
Publisher URL: http://dx.doi.org/10.1088/0264-9381/27/3/035011
Peer reviewed