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Friedmann–Lemaître–Robertson–Walker metric
About: Friedmann–Lemaître–Robertson–Walker metric is a research topic. Over the lifetime, 4113 publications have been published within this topic receiving 87752 citations. The topic is also known as: FLRW metric.
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TL;DR: In this paper, the Brans-Dicke equations with the cosmological constant were studied and exact solutions in the spatially flat Robertson-Walker metric in the matter-dominated universe were presented.
Abstract: The Brans-Dicke equations with the cosmological constant are studied. We present exact solutions in the spatially flat Robertson-Walker metric in the matter-dominated universe. A brief discussion on this cosmology is given.
56 citations
TL;DR: A brief history of the cosmological constant in the equations of general relativity is presented in this paper, with particular attention paid to a misunderstanding by Einstein of both its function as a repulsive force and new vacuum state rather than the relativistic analog of an exponential potential cutoff he had introduced.
Abstract: A brief history of the cosmological constant in the equations of general relativity is presented. Particular attention is paid to (a) a misunderstanding by Einstein of both its function as a repulsive force and new vacuum state rather than the relativistic analog of an exponential potential cutoff he thought he had introduced and to (b) a common misunderstanding of the function of the cosmological constant.
56 citations
TL;DR: In this article, the authors examined the possibility that there exist special scalar-tensor theories of gravity with completely nonsingular FRW solutions, and they concluded that the singularity cannot be entirely removed, but only be made invisible to most, but not all, probes in the theory.
Abstract: In this article, we examine the possibility that there exist special scalar-tensor theories of gravity with completely nonsingular FRW solutions. Our investigation in fact shows that while most probes living in such a universe never see the singularity, gravity waves always do. This is because they couple to both the metric and the scalar field, in a way which effectively forces them to move along null geodesics of the Einstein conformal frame. Since the metric of the Einstein conformal frame is always singular for configurations where matter satisfies the energy conditions, the gravity wave world lines are past inextendable beyond the Einstein frame singularity, and hence the geometry is still incomplete, and thus singular. We conclude that the singularity cannot be entirely removed, but only be made invisible to most, but not all, probes in the theory.
56 citations
TL;DR: In this paper, the effects of inhomogeneities on light propagation in a flat Λ cold dark matter (ΛCDM) background were studied, where the authors use exact solutions of Einstein's equations as derived by Meures & Bruni where, starting from small fluctuations, inhomogenities arise from a standard growing mode and become nonlinear.
Abstract: Motivated by the dawn of precision cosmology and the wealth of forthcoming high-precision and volume galaxy surveys, in this paper we study the effects of inhomogeneities on light propagation in a flat Λ cold dark matter (ΛCDM) background. To this end we use exact solutions of Einstein’s equations as derived by Meures & Bruni where, starting from small fluctuations, inhomogeneities arise from a standard growing mode and become non-linear. While the matter distribution in these models is necessarily idealized, there is still enough freedom to assume an arbitrary initial density profile along the line of sight. We can therefore model overdensities and voids of various sizes and distributions, e.g. single harmonic sinusoidal modes, coupled modes and more general distributions in a ΛCDM background. Our models allow for an exact treatment of the light-propagation problem, so that the results are unaffected by approximations and unambiguous. Along lines of sight with density inhomogeneities which average out on scales less than the Hubble radius, we find the distance–redshift relation to diverge negligibly from the Friedmann–Lemaitre–Robertson–Walker (FLRW) result. On the contrary, if we observe along lines of sight which do not have the same average density as the background, we find large deviations from the FLRW distance–redshift relation. Hence, a possibly large systematic might be introduced into the analysis of cosmological observations, e.g. supernovae, if we observe along lines of sight which are typically more or less dense than the average density of the Universe. In turn, this could lead to wrong parameter estimation: even if the cosmological principle is valid, the identification of the true FLRW background in an inhomogeneous universe may be more difficult than usually assumed.
56 citations
TL;DR: In this article, the Szekeres models were used to fit supernova combined data sets and showed that with a choice of the spatial curvature function that is guided by current observations, the models fit the supernova data almost as well as the LCDM model.
Abstract: We use the Szekeres inhomogeneous relativistic models in order to fit supernova combined data sets. We show that with a choice of the spatial curvature function that is guided by current observations, the models fit the supernova data almost as well as the LCDM model without requiring a dark energy component. The Szekeres models were originally derived as an exact solution to Einstein's equations with a general metric that has no symmetries and are regarded as good candidates to model the true lumpy universe that we observe. The null geodesics in these models are not radial. The best fit model found is also consistent with the requirement of spatial flatness at CMB scales. The first results presented here seem to encourage further investigations of apparent acceleration using various inhomogeneous models and other constraints from CMB and large structure need to be explored next.
55 citations