Decaying dark energy in higher-dimensional gravity

Abstract

Aims. We use data from observational cosmology to put constraints on higher-dimensional extensions of general relativity in which the effective four-dimensional dark-energy density (or cosmological "constant") decays with time.Methods. In particular we study the implications of this decaying dark energy for the age of the universe, large-scale structure formation, big-bang nucleosynthesis and the magnitude-redshift relation for type Ia supernovae. Results. Two of these tests (age and the magnitude-redshift relation) place modest lower limits on the free parameter of the theory, a cosmological length scale L akin to the de Sitter radius. These limits will improve if experimental uncertainties on supernova magnitudes can be reduced around z ∼ 1.

Puzzles of Physics

“…which on multiplication by 2 c gives the and more detailed models show that Λ may have been formally infinite at the start of the universe and have diminished over our 9 13 10 × yr history to the small value we observe today (Overduin 1999;Overduin, Wesson and Mashhoon 2007). Other models go further, and suggest that the cosmological 'constant' is in fact just the average value over large scales for a field that fluctuates in space.…”

Inducing the Cosmological Constant from Five-Dimensional Weyl Space

“…Assuming that the induced matter configuration given by (34) is that of a perfect fluid, as viewed by four-dimensional comoving observers located at the hypersurface 0 , we can define the energy density ρ (I M) and pressure P (I M) for the induced matter by ρ (I M) = T (I M) t t and P (I M) = −T (I M)r r respectively. Thus using (33) the 4D field equations (30) become…”

“…However, it seems interesting to investigate the subject when the geometry of the embedding space has more degrees of freedom, as in the case of Weyl geometry, perhaps the simplest generalization of Riemannian geometry [32,33]. It turns out then that when we go down from 5D to 4D, as in the space-time-matter theory, the Weyl field may contribute both to the induced energy-tensor as well as to the cosmological constant , or more generally, to a time-dependent cosmological function (t) [34].…”

Cosmology With Decaying Dark Energy and Cosmological "Constant"

“…A decaying Λ is consistent with the age of the universe 5,6 and our model agrees with astrophysical data, including those on supernovae. 11,12 It preserves much of the conventional physics associated with the generation of the microwave background, nucleosynthesis and the formation of structure. However, it adds certain elements, particularly in the last area.…”

“…9,10 These properties will be seen to lead to a better understanding of astrophysical data and the early universe, 11,12 while providing hints about particle physics.…”