Year: 2005
Type: article
Abstract: For a broad range of parameter values, braneworld models display a remarkable property which we call cosmic mimicry . Cosmic mimicry is characterized by the fact that, at low redshifts, the Hubble parameter in the braneworld model is virtually indistinguishable from that in the LCDM (Λ+cold dark matter) cosmology. An important point to note is that the Ω m parameters in the braneworld model and in the LCDM cosmology can nevertheless be quite different. Thus, at high redshifts (early times), the braneworld asymptotically expands like a matter-dominated universe with the value of Ω m inferred from the observations of the local matter density. At low redshifts (late times), the braneworld model behaves almost exactly like the LCDM model but with a renormalized value of the cosmological density parameter Ω m LCDM . The value of Ω m LCDM is smaller (larger) than Ω m in the braneworld model with positive (negative) brane tension. The redshift which characterizes cosmic mimicry is related to the parameters in the higher-dimensional braneworld Lagrangian. Cosmic mimicry is a natural consequence of the scale dependence of gravity in braneworld models. The change in the value of the cosmological density parameter (from Ω m at high z to Ω m LCDM at low z ) is shown to be related to the spatial dependence of the effective gravitational constant G eff in braneworld theory. A subclass of mimicry models lead to an older age of the universe and also predict a redshift of reionization which is lower than in the LCDM cosmology. These models might therefore provide a background cosmology which is in better agreement both with the observed quasar abundance at and with the large optical depth to reionization measured by the Wilkinson microwave anisotropy probe.
Authors: Varun Sahni, Yuri Shtanov, Alexander Viznyuk
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2050821465