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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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Journal ArticleDOI
TL;DR: In this article, a phase-plane analysis of the flow defined by the equations of motion of a FRW Universe filled with a tachyonic fluid plus a barotropic one is performed.
Abstract: We perform a thorough phase-plane analysis of the flow defined by the equations of motion of a FRW Universe filled with a tachyonic fluid plus a barotropic one. The tachyon potential is assumed to be of inverse square form, thus allowing for a two-dimensional autonomous system of equations. The Friedmann constraint, combined with a convenient choice of coordinates, renders the physical state compact. We find the fixed-point solutions, and discuss whether or not they represent attractors. The way the two fluids contribute at late times to the fractional energy density depends on how fast the barotropic fluid redshifts. If it does it fast enough, the tachyonic fluid takes over at late times, but if the opposite happens, the situation will not be completely dominated by the barotropic fluid; instead there will be a residual non-negligible contribution from the tachyon subject to restrictions coming from nucleosynthesis.

163 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigate quintom cosmology in FRW universes using isomorphic models consisting of three coupled oscillators, one of which carries negative kinetic energy, and obtain their qualitative characteristics as well as their quantitative asymptotic behavior.

163 citations

Journal ArticleDOI
TL;DR: In this paper, an exact Swiss-cheese model of the universe, where inhomogeneous LTB patches are embedded in a flat FLRW background, was studied to see how observations of distant sources are affected.
Abstract: We study an exact Swiss-cheese model of the universe, where inhomogeneous LTB patches are embedded in a flat FLRW background, in order to see how observations of distant sources are affected. We focus mainly on the redshift, both perturbatively and non-perturbatively: the net effect given by one patch is suppressed by (L/RH)3 (where L is the size of one patch and RH is the Hubble radius). We disentangle this effect from the Doppler term (which is much larger and has been used recently (Biswas et al 2007 J. Cosmol. Astropart. Phys. JCAP12(2007)017 [astro-ph/0606703]) to try to fit the SN curve without dark energy) by making contact with cosmological perturbation theory. Then, the correction to the angular distance is discussed analytically and estimated to be larger, , perturbatively and non-perturbatively (although it should go to zero after angular averaging).

160 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compare two forms of the Robertson-Walker (RW) metric written in (the traditional) comoving coordinates, and a set of observer-dependent coordinates, first for the well-known de Sitter universe containing only dark energy, and then for a newly derived form of the RW metric, for a universe with dark energy and matter.
Abstract: The cosmological principle, promoting the view that the Universe is homogeneous and isotropic, is embodied within the mathematical structure of the Robertson‐Walker (RW) metric. The equations derived from an application of this metric to the Einstein Field Equations describe the expansion of the Universe in terms of comoving coordinates, from which physical distances may be derived using a time-dependent expansion factor. These coordinates, however, do not explicitly reveal the properties of the cosmic space‐time manifested in Birkhoff’s theorem and its corollary. In this paper, we compare two forms of the metric ‐ written in (the traditional) comoving coordinates, and a set of observer-dependent coordinates ‐ first for the well-known de Sitter universe containing only dark energy, and then for a newly derived form of the RW metric, for a universe with dark energy and matter. We show that Rindler’s event horizon ‐ evident in the comoving system ‐ coincides with what one might call the ‘curvature horizon’ appearing in the observer-dependent frame. The advantage of this dual prescription of the cosmic space‐time is that with the latest Wilkinson Microwave Anisotropy Probe results, we now have a much better determination of the Universe’s mass-energy content, which permits us to calculate this curvature with unprecedented accuracy. We use it here to demonstrate that our observations have probed the limit beyond which the cosmic curvature prevents any signal from having ever reached us. In the case of de Sitter, where the mass-energy density is a constant, this limit is fixed for all time. For a universe with a changing density, this horizon expands until de Sitter is reached asymptotically, and then it too ceases to change.

159 citations

Journal ArticleDOI
TL;DR: Higher-dimensional braneworld models which contain both bulk and brane curvature terms in the action admit cosmological singularities of rather unusual form and nature as mentioned in this paper, which can occur both during the contracting as well as the expanding phase.
Abstract: Higher-dimensional braneworld models which contain both bulk and brane curvature terms in the action admit cosmological singularities of rather unusual form and nature. These 'quiescent' singularities, which can occur both during the contracting as well as the expanding phase, are characterized by the fact that while the matter density and Hubble parameter remain finite, all higher derivatives of the scale factor ( etc) diverge as the cosmological singularity is approached. The singularities are the result of the embedding of the (3 + 1)-dimensional brane in the bulk and can exist even in an empty homogeneous and isotropic (FRW) universe. The possibility that the present universe may expand into a singular state is discussed.

157 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023150
2022352
2021196
2020204
2019214
2018191