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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 article, the authors explore observables in a lattice Universe described by a recently found solution to the Einstein field equations, and they find a condition on the compactness of the objects at the centre of each cell under which corrections to the FLRW observables remain small.
Abstract: We explore observables in a lattice Universe described by a recently found solution to Einstein field equations. This solution models a regular lattice of evenly distributed objects of equal masses. This inhomogeneous solution is perturbative, and, up to second order in a small parameter, it expands at a rate exactly equal to the one expected in a dust dominated Friedmann-Lema\^itre-Robertson-Walker (FLRW) model with the equivalent, smoothed, energy density. Therefore, the kinematics of both cosmologies are identical up to the order of perturbation studied. Looking at the behaviour of the redshift and angular distance, we find a condition on the compactness of the objects at the centre of each cell under which corrections to the FLRW observables remain small, i.e. of order of a few percents at most. Nevertheless, we show that, if this condition is violated, i.e. if the objects are too compact, our perturbative scheme breaks down as far as the calculations of observables are concerned, even though the kinematics of the lattice remains identical to its FLRW counter-part (at the perturbative order considered). This may be an indication of an actual fitting problem, i.e. a situation in which the FLRW model obtained from lightcone observables does not correspond to the FLRW model obtained by smoothing the spatial distribution of matter. Fully non-perturbative treatments of the observables will be necessary to answer that question.
48 citations
TL;DR: In this paper, the dynamics of a D3-brane propagating in the vicinity of k coincident NS5 branes were studied, and it was shown that when $g_s$ is small, there exists a regime in which dynamics of the Dbrane is governed by Dirac-Born-Infeld action while higher order derivative in the expansion can not be neglected.
Abstract: We study dynamics of a D3-brane propagating in the vicinity of k coincident NS5 branes. We show that when $g_s$ is small, there exists a regime in which dynamics of the D-brane is governed by Dirac-Born-Infeld action while higher order derivative in the expansion can not be neglected. This leads to a restriction on how fast scalar field may roll. We analyze the motion of a rolling scalar field in this regime, and extend the analysis to cosmological systems obtained by coupling this type of field theory to four dimensinal gravity. It also leads to some FRW cosmologies, some of which are related to those obtained with tachyon matter.
48 citations
TL;DR: The authors showed that McVittie geometry, which describes a black hole embedded in a FLRW universe, not only solves the Einstein equations but also remains as a non-deformable solution of f(T) gravity.
Abstract: We show that McVittie geometry, which describes a black hole embedded in a FLRW universe, not only solves the Einstein equations but also remains as a non-deformable solution of f(T) gravity. This search for GR solutions that survive in f(T) gravity is facilitated by a null tetrad approach. We also show that flat FLRW geometry is a consistent solution of f(T) dynamical equations not only for $$T=-6H^{2}$$
but also for $$T=0$$
, which could be a manifestation of the additional degrees of freedom involved in f(T) theories.
48 citations
TL;DR: In this article, an entropy-corrected holographic dark energy (ECHDE) was proposed to explain the dark energy-dominated universe with the help of quantum corrections to the entropy-area relation in the setup of loop quantum cosmology.
Abstract: An entropy-corrected holographic dark energy (ECHDE) was recently proposed to explain the dark energy-dominated universe with the help of quantum corrections to the entropy–area relation in the setup of loop quantum cosmology. Using this new definition, we investigate its thermodynamical features including entropy and energy conservation. We describe the thermodynamical interpretation of the interaction between ECHDE and dark matter in a non-flat universe. We obtain a relation between the interaction term of the dark components and thermal fluctuation. Our study further generalizes the earlier works86, 87 in this direction.
48 citations
TL;DR: In this paper, the authors investigated the dynamics of a flat FRW cosmological model with a non-minimally coupled scalar field with the coupling term ξRψ2 in the action.
Abstract: In this publication we investigate dynamics of a flat FRW cosmological model with a non-minimally coupled scalar field with the coupling term ξRψ2 in the scalar field action. The quadratic potential function V(ψ) ∝ ψ2 is assumed. All the evolutional paths are visualized and classified in the phase plane, at which the parameter of non-minimal coupling ξ plays the role of a control parameter. The fragility of global dynamics with respect to changes of the coupling constant is studied in details. We find that the future big rip singularity appearing in the phantom scalar field cosmological models can be avoided due to non-minimal coupling constant effects. We have shown the existence of a finite scale factor singular point (future or past) where the Hubble function as well as its first cosmological time derivative diverge.
48 citations