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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, a simple and straightforward averaging procedure is introduced, which is a generalization of one which is commonly used in electrodynamics, and show that it possesses all the characteristics we require for linearized averaging in general relativity and cosmology for weak-field and perturbed FLRW situations.
Abstract: We introduce a simple and straightforward averaging procedure, which is a generalization of one which is commonly used in electrodynamics, and show that it possesses all the characteristics we require for linearized averaging in general relativity and cosmology — for weak-field and perturbed FLRW situations. In particular, we demonstrate that it yields quantities which are approximately tensorial in these situations, and that its application to an exact FLRW metric yields another FLRW metric, to first-order in integrals over the local coordinates. Finally, we indicate some important limits of any linearized averaging procedure with respect to cosmological perturbations which are the result of averages over large amplitude small and intermediate scale inhomogeneities, and show our averaging procedure can be approximately implemented by that of Zotov and Stoeger in these cases.
20 citations
TL;DR: In this paper, a study of universal thermodynamics is done in the framework of RSII brane model and DGP brane scenario, where the universe is chosen as FRW model bounded by apparent or event horizon.
Abstract: A study of Universal thermodynamics is done in the framework of RSII brane model and DGP brane scenario. The Universe is chosen as FRW model bounded by apparent or event horizon. Assuming extended Hawking temperature on the horizon, the unified first law is examined for perfect fluid (with constant equation of state) and Modified Chaplygin Gas model. As a result there is a modification of Bekenstein entropy on the horizons. Further the validity of the generalized second law of thermodynamics and thermodynamical equilibrium are also investigated.
20 citations
TL;DR: In this article, the properties of FRW and doubled spherically symmetric metric of double field theory are studied. But the authors focus on the generalized Lie derivative, which is the extension of the Courant bracket.
Abstract: Double field theory (DFT) offers a manifest O(D, D) formulation for massless closed string field theory with both momentum and winding excitations. The gauge symmetry is defined by the generalized Lie derivative which is the extension of the Courant bracket. In this work, we solve and study the properties of FRW (Friedmann-Robertson-Walker) and doubled spherically symmetric metric of DFT.
20 citations
TL;DR: In this article, a particle count treatment of gravitons and subsequent entropy generation was proposed to explain/justify a value of entropy of the order of S～106-107 at the very onset of inflation.
Abstract: Based upon Alcubierre’s formalism about energy flux of gravitational waves, as well as Saunder’s treatment of temperature dependence of the Hubble parameter in the early universe, we initiate a particle count treatment of gravitons, and subsequent entropy generation which gives, via the standard model treatment of the FRW metric a way to explain/justify a value of entropy of the order of S～106-107 at the very onset of inflation.
20 citations
TL;DR: In this article, it was shown that singular behavior does not occur for a class of nonlinear generalizations of the electromagnetic theory for strong fields, and a new mathematical model was proposed for which the analytical nonsingular extension of FRW solutions is obtained by using the nonlinear magnetic monopole fields.
Abstract: Despite impressive phenomenological success, cosmological models are incomplete without an understanding of what happened at the big bang singularity. Maxwell electrodynamics, considered as a source of the classical Einstein field equations, leads to the singular isotropic Friedmann solutions. In the context of Friedmann–Robertson–Walker (FRW) spacetime, we show that singular behavior does not occur for a class of nonlinear generalizations of the electromagnetic theory for strong fields. A new mathematical model is proposed for which the analytical nonsingular extension of FRW solutions is obtained by using the nonlinear magnetic monopole fields.
20 citations