Bibliographies thématiques / Friedmann-Robertson-Walker background equations

Littérature scientifique sur le sujet « Friedmann-Robertson-Walker background equations »

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Publié le 14 mars 2023

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Articles de revues sur le sujet "Friedmann-Robertson-Walker background equations"

Shchigolev, Victor. « An approximate solution of the Yang - Mills equation on a spatially flat FRW cosmological background ». International Journal of Physical Research 7, n^o 2 (21 septembre 2019) : 100. http://dx.doi.org/10.14419/ijpr.v7i2.29775.

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In this paper, an approximate solution for the Yang - Mills equation in a spatially flat Friedmann-Robertson-Walker universe is obtained. For this purpose, the well known method of solution of non-linear differential equations is used, viz. the homotopy perturbations method. This method has been developed as effective technique for solving different non-linear problems. Here, this method allowed us to obtain approximate solution for the essentially non-linear equation for the SO3 Yang-Mills fields on the curved space-time background of the spatially flat Friedmann-Robertson-Walker universe.

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Liu, Jianwen, Ruifang Wang et Fabao Gao. « Dynamics of a Cosmological Model in f(R,T) Gravity : I. On Invariant Planes ». Universe 8, n^o 7 (3 juillet 2022) : 365. http://dx.doi.org/10.3390/universe8070365.

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Under the background of perfect fluid and flat Friedmann–Lemaître–Robertson–Walker (FLRW) space-time, this paper mainly describes the dynamics of the cosmological model constructed in f(R,T) gravity on three invariant planes, by using the singularity theory and Poincaré compactification in differential equations.

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Paliathanasis, Andronikos. « Painlevé Analysis of the Cosmological Field Equations in Weyl Integrable Spacetime ». Universe 8, n^o 7 (23 juin 2022) : 345. http://dx.doi.org/10.3390/universe8070345.

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We apply a singularity analysis to investigate the integrability properties of the gravitational field equations in Weyl Integrable Spacetime for a spatially flat Friedmann–Lemaître–Robertson–Walker background spacetime induced by an ideal gas. We find that the field equations possess the Painlevé property in the presence of the cosmological constant, and the analytic solution is given by a left Laurent expansion.

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Coley, A. A., et B. O. J. Tupper. « Two-fluid Friedmann–Robertson–Walker cosmologies and their numerical predictions ». Canadian Journal of Physics 64, n^o 2 (1 février 1986) : 204–9. http://dx.doi.org/10.1139/p86-036.

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Friedmann–Robertson–Walker models satisfying the Einstein field equations for a combination of two fluids, one of which is a comoving perfect fluid with the radiation equation of state [Formula: see text], representing the cosmic microwave background, are discussed. Existing models, in which the second fluid is a comoving perfect fluid, are reviewed and their numerical predictions calculated. These models are generalized by considering the case in which the second fluid is an imperfect fluid. This fluid is necessarily noncomoving, the tilt representing the motion of the local supercluster of galaxies relative to the cosmic microwave background. The numerical predictions of one such model are calculated and are found to be in excellent agreement with observation.

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LAHIRI, JOYDEV, et GAUTAM BHATTACHARYA. « A COVARIANT APPROACH TO THE GENERALIZED MULTI-INFLATON COSMOLOGICAL PERTURBATION ». International Journal of Modern Physics A 24, n^o 20n21 (20 août 2009) : 3893–916. http://dx.doi.org/10.1142/s0217751x09044231.

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Following the formalism developed in Astrophys. J.375, 443 (1991), differential equations for the gauge invariant scalar part of the metric perturbation in the Friedmann–Robertson–Walker background with multiple inflatons with arbitrary field metric are obtained without any specific choice of gauge. Subsequently, an algorithm for the solution of these equations in the slow-roll approximation is given without any prior choice of the basis system in the field manifold. Vector and tensor perturbations are also briefly reviewed.

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Amani, Ali R. « The bouncing cosmology with F(R) gravity and its reconstructing ». International Journal of Modern Physics D 25, n^o 06 (mai 2016) : 1650071. http://dx.doi.org/10.1142/s0218271816500711.

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In this paper, we study [Formula: see text] gravity by Hu–Sawicki model in Friedmann–Lemaître–Robertson–Walker (FLRW) background. The Friedmann equations are calculated by modified gravity action, and then the obtained Friedmann equations are written in terms of standard Friedmann equations. Next, the behavior of bouncing cosmology is investigated in the modified gravity model, i.e. this behavior can solve the problem of nonsingularity in standard big bang cosmology. We plot the cosmological parameters in terms of cosmic time and then the bouncing condition is investigated. In what follows, we reconstruct the modified gravity by redshift parameter, and also graphs of cosmological parameters are plotted in terms of redshift, in which the figures show us an accelerated expansion of universe. Finally, the stability of the scenario is investigated by a function as sound speed, and the graph of sound speed versus redshift shows us that there is the stability in late-time.

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Yılmaz, Nejat Tevfik. « Effective fluid FLRW cosmologies of minimal massive gravity ». Modern Physics Letters A 30, n^o 18 (25 mai 2015) : 1550087. http://dx.doi.org/10.1142/s021773231550087x.

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By using a solution ansatz we partially decouple the metric and the Stückelberg sectors of the minimal massive gravity (MMGR). In this scheme for a diagonal physical metric we find the general solutions for the scalars of the theory and the particular fiducial (background) metric which leads to these solutions. Then we adopt this general formalism to construct the derivation of new Friedmann–Lemaitre–Robertson–Walker (FLRW) cosmologies of the theory in the presence of a so-called effective ideal fluid which arises from our solution ansatz as a modifying, non-physical source for the Einstein and the corresponding Friedmann equations.

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Pal, Subhajyoti, Sudip Mishra et Subenoy Chakraborty. « Dynamical system analysis of a nonminimally coupled scalar field ». International Journal of Modern Physics D 28, n^o 15 (novembre 2019) : 1950173. http://dx.doi.org/10.1142/s0218271819501736.

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This paper deals with a nonminimally coupled scalar field in the background of homogeneous and isotropic Friedmann–Lemaître–Robertson–Walker (FLRW) flat spacetime. As Einstein field equations are coupled second-order nonlinear differential equations, it is very hard to find exact solutions. By suitable choice of variables, we transform Einstein field equations to an autonomous system and critical points are determined. We use center manifold theory to characterize nonhyperbolic critical points and are found to be saddle in nature. We discuss possible bifurcation scenarios, which indicate the existence of the cosmological bouncing model.

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Paliathanasis, Andronikos, et Genly Leon. « Cosmological solutions in Hořava-Lifshitz scalar field theory ». Zeitschrift für Naturforschung A 75, n^o 6 (26 mai 2020) : 523–32. http://dx.doi.org/10.1515/zna-2020-0003.

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AbstractWe perform a detailed study of the integrability of the Hořava-Lifshitz scalar field cosmology in a Friedmann-Lemaître-Robertson-Walker background space-time. The approach we follow to determine the integrability is that of singularity analysis. More specifically, we test whether the gravitational field equations possess the Painlevé property. For the exponential potential of the scalar field, we are able to perform an analytic explicit integration of the field equations and write the solution in terms of a Laurent expansion and more specifically write the solution in terms of right Painlevé series.

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Dutta, Malay Krishna, et B. Modak. « Can Noether symmetry in modified f(G) gravity always yield cosmic evolution ? » Modern Physics Letters A 32, n^o 11 (7 avril 2017) : 1750046. http://dx.doi.org/10.1142/s0217732317500468.

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We discuss Noether symmetry approach in the modified theory of gravity with Gauss–Bonnet (GB) interaction-f(G) including an ideal fluid in Friedmann–Lemaître–Robertson–Walker (FLRW) background. It yields functional form of f(G) from the symmetry. The existence of Noether symmetry gives the scale factor in two cases, but these are not satisfied by field equations in general. In another case, the solution of field equations shows late-time transition to an accelerating expansion when matter is dust, however the solution including dust and radiation is always in accelerating era.

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Chapitres de livres sur le sujet "Friedmann-Robertson-Walker background equations"

Carlip, Steven. « Cosmology ». Dans General Relativity, 92–100. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198822158.003.0011.

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Starting with the assumptions of homogeneity and isotropy, the cosmological solutions of the Einstein field equations—the Friedmann-Lemaitre-Robertson-Walker metrics—are derived. After a discussion of constant curvature metrics and the topology of the Universe, the chapter moves on to discuss observational implications: expansion of the Universe, cosmological red shift, primordial nucleosynthesis, the cosmic microwave background, and primordial perturbations. The chapter includes a brief discussion of de Sitter and anti-de Sitter space and an introduction to inflation.

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