Topic
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 cosmological perturbations around FLRW solutions to non-linear massive gravity with a new effective coupling to matter were investigated, and it was shown that all five degrees of freedom in the gravity sector propagate on generic self-accelerating FLRW backgrounds.
Abstract: We investigate the cosmological perturbations around FLRW solutions to non- linear massive gravity with a new effective coupling to matter proposed recently. Unlike the case with minimal matter coupling, all five degrees of freedom in the gravity sector propagate on generic self-accelerating FLRW backgrounds. We study the stability of the cosmological solutions and put constraints on the parameters of the theory by demanding the correct sign for the kinetic terms for scalar, vector and tensor perturbations.
55 citations
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TL;DR: In this paper, the dynamics of homogeneous isotropic FRW cosmologies with positive spatial curvature in $f(R)$-gravity were studied, paying special attention to the existence of Einstein static models.
Abstract: We study the dynamics of homogeneous isotropic FRW cosmologies with positive spatial curvature in $f(R)$-gravity, paying special attention to the existence of Einstein static models and only study forms of $f(R)=R^n$ for which these static models have been shown to exist. We construct a compact state space and identify past and future attractors of the system and recover a previously discovered future attractor corresponding to an expanding accelerating model. We also discuss the existence of universes which have both a past and future bounce, a phenomenon which is absent in General Relativity.
55 citations
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TL;DR: In this paper, the authors propose a metrique de type Friedman-Robertson-Walker (FRW) for the element a symetrie spherique and dimension elevee.
Abstract: En partant d'un modele de fluide parfait homogene avec ρ = ρ(t) et p = p(t), on montre que la metrique de type Friedman-Robertson-Walker est l'unique solution pour l'element a symetrie spherique et dimension elevee. Sous l'hypothese d'une equation d'etat p = mρ, les solutions explicites du facteur d'echelle sont etablies et les implications cosmologiques sont discutees. Quelques parametres astrophysiques sont calcules et compares avec les cas analogues a 4 dimensions.
55 citations
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TL;DR: In this paper, the evolution of the scale factor in such a construction must be governed not by the standard Einstein equations for the FLRW metric, but by the modified Friedmann equations derived by Buchert (Gen Relat Gravit 32:105, 2000; 33:1381, 2001).
Abstract: The present matter density of the Universe, while highly inhomogeneous on small scales, displays approximate homogeneity on large scales. We propose that whereas it is justified to use the Friedmann–Lemaitre–Robertson–Walker (FLRW) line element (which describes an exactly homogeneous and isotropic universe) as a template to construct luminosity distances in order to compare observations with theory, the evolution of the scale factor in such a construction must be governed not by the standard Einstein equations for the FLRW metric, but by the modified Friedmann equations derived by Buchert (Gen Relat Gravit 32:105, 2000; 33:1381, 2001) in the context of spatial averaging in Cosmology. Furthermore, we argue that this scale factor, defined in the spatially averaged cosmology, will correspond to the effective FLRW metric provided the size of the averaging domain coincides with the scale at which cosmological homogeneity arises. This allows us, in principle, to compare predictions of a spatially averaged cosmology with observations, in the standard manner, for instance by computing the luminosity distance versus red-shift relation. The predictions of the spatially averaged cosmology would in general differ from standard FLRW cosmology, because the scale-factor now obeys the modified FLRW equations. This could help determine, by comparing with observations, whether or not cosmological inhomogeneities are an alternative explanation for the observed cosmic acceleration.
54 citations
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TL;DR: In this paper, the scale invariant two-measure field theory (TMT) model is explored in detail in the context of closed FRW cosmology and shown to allow stable emerging universe solutions.
54 citations