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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 thermodynamics of a FRW universe within a proposed Modified Dispersion Relations (MDR) in an extra dimensional model universe are compared with the well-known results for the thermodynamic properties of FRW universes in a generalized uncertainty principle (GUP) setup.
61 citations
TL;DR: In this article, a handful of local and non-local measures of acceleration in a variety of inhomogeneous cosmological models were investigated, and it was shown that the acceleration inferred from observations of the distance-redshift relation is closely related to the acceleration of the spatially averaged universe, but does not necessarily bear any resemblance to the average of the local acceleration of spacetime itself.
Abstract: Current cosmological observations, when interpreted within the framework of a homogeneous and isotropic Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) model, strongly suggest that the Universe is entering a period of accelerating expansion. This is often taken to mean that the expansion of space itself is accelerating. In a general spacetime, however, this is not necessarily true. We attempt to clarify this point by considering a handful of local and nonlocal measures of acceleration in a variety of inhomogeneous cosmological models. Each of the chosen measures corresponds to a theoretical or observational procedure that has previously been used to study acceleration in cosmology, and all measures reduce to the same quantity in the limit of exact spatial homogeneity and isotropy. In statistically homogeneous and isotropic spacetimes, we find that the acceleration inferred from observations of the distance-redshift relation is closely related to the acceleration of the spatially averaged universe, but does not necessarily bear any resemblance to the average of the local acceleration of spacetime itself. For inhomogeneous spacetimes that do not display statistical homogeneity and isotropy, however, we find little correlation between acceleration inferred from observations and the acceleration of the averaged spacetime. This shows that observations made in an inhomogeneous universe can imply acceleration without the existence of dark energy.
61 citations
TL;DR: In this paper, the cosmological dynamics of multiple tachyon fields with inverse square potentials were investigated, and the stability of the solutions was investigated only for the case of two tachyan fields and found that the potential - kinetic scaling solution is a global attractor.
Abstract: We investigate the cosmological dynamics of multiple tachyon fields with inverse square potentials. A phase-space analysis of the spatially flat FRW models shows that there exist power-law cosmological scaling solutions. We study the stability of the solutions only for the case of two tachyon fields and find that the potential - kinetic- scaling solution is a global attractor. However, in the presence of a barotropic fluid the solution is an attractor only in one region of the parameter space, and the tracking solution is an attractor in the other region. We briefly discuss the physical consequences of these results.
61 citations
TL;DR: In this paper, the cosmological constant with respect to the velocity of light, Planck and Newton gravitational constants has been derived from distant supernovae observations, and it is shown that the current value remarkably agrees with the value indicated by distant supernova observations, i.e. of the order of the critical density.
Abstract: We advance the viewpoint that, only relevant modes of the vacuum fluctuations, namely, with wavelengths conditioned by the size, homogeneity, geometry and topology of the Universe, do contribute to the cosmological constant. A formula is derived which relates the cosmological constant with the size of the Universe and the three fundamental constants: the velocity of light, Planck and Newton gravitational constants. Then the current value of the cosmological constant remarkably agrees with the value indicated by distant supernovae observations, i.e. of the order of the critical density. Thus the cosmological constant had to be smaller than the matter density in the past and will be bigger in the future.
61 citations
TL;DR: In this article, the APS construction of the quantum Hamiltonian is analyzed under the assumption that the cosmological constant is a constant, and the essential self-adjointness of the operator whose square-root defines in [1] is proved.
Abstract: The flat Friedman?Robertson?Walker (FRW) model coupled to the massless scalar field according to the improved, background scale-independent version of Ashtekar, Paw?owski and Singh [1] is considered. The core of the theory is addressed directly: the APS construction of the quantum Hamiltonian is analyzed under the assumption that the cosmological constant ? ? 0. We prove the essential self-adjointness of the operator whose square-root defines in [1] the quantum Hamiltonian operator and therefore provide the explicit definition. If ? 0 being some constants) plus a trace class operator.
61 citations