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.

Averaging of a locally inhomogeneous realistic universe.

Abstract: We present an averaging scheme in general relativity which allows us to study the effect of local inhomogeneity on the global behavior of the universe. The scheme uses 3+1 splitting of spacetime and introduces Isaacson averaging on the spatial hypersurface to get the averaged geometry. As a result of the averaging, the Friedmann-Robertson-Walker (FWR) geometry is derived in the first-order approximation for a wide class of inhomogeneous nonlinear matter distribution. The deviation from the FRW expansion is derived to the next order in terms of the anisotropic distribution of an effective stress-energy tensor. Using a simple model of inhomogeneity we show that the average effect of the inhomogeneity behaves like a negative spatial curvature term and thus has a tendency to extend the age of the universe. \textcopyright{} 1996 The American Physical Society.

Model of a decaying cosmological constant.

Abstract: A theoretical model is proposed for decay of the cosmological constant, allowing a natural interpretation that the cosmological constant is small at present simply because our Universe is old. The model can be made consistent with inflation, the observed time nonvariability of the gravitational constant, as well as evidence for the standard cosmology. The crucial ingredients are an extended theory of a scalar field and a careful analysis of conformal transformations.

Dynamics in nonlocal linear models in the Friedmann-Robertson-Walker metric

Abstract: A general class of cosmological models driven by a nonlocal scalar field inspired by the string field theory is studied. Using the fact that the considering linear nonlocal model is equivalent to an infinite number of local models we have found an exact special solution of the nonlocal Friedmann equations. This solution describes a monotonically increasing Universe with the phantom dark energy.

The nonlinear future stability of the FLRW family of solutions to the Euler-Einstein system with a positive cosmological constant

Abstract: In this article, we study small perturbations of the family of Friedmann–Lemaitre–Robertson–Walker cosmological background solutions to the 1 + 3 dimensional Euler–Einstein system with a positive cosmological constant. These background solutions describe an initially uniform quiet fluid of positive energy density evolving in a spacetime undergoing accelerated expansion. Our nonlinear analysis shows that under the equation of state $${p = c^2_s \rho}$$ , $${0 < c^2_s < 1/3}$$ , the background solutions are globally future-stable. In particular, we prove that the perturbed spacetime solutions, which have the topological structure $${[0,\infty) \times \mathbb{T}^3}$$ , are future-causally geodesically complete. These results are extensions of previous results derived by the author in a collaboration with I. Rodnianski, in which the fluid was assumed to be irrotational. Our novel analysis of a fluid with non-zero vorticity is based on the use of suitably defined energy currents.