Brane Universes Tested by Supernovae

Abstract

We discuss observational constrains coming from supernovae Ia [3] imposed on the behaviour of the Randall-Sundrum models. In the case of dust matter on the brane, the difference between the best-fit general relativistic model with a Λ-term [3] and the best-fit brane models becomes detectable for redshifts z > 0.6. It is interesting that brane models predict brighter galaxies for such redshifts which is in agreement with the measurement of the z = 1.7 supernova [6] and with the New Data from the High Z Supernovae Search Team [7]. We also demonstrate that the fit to supernovae data can also be obtained, if we admit the "super-negative" dark energy p = −(4/3)̺ on the brane, where the dark energy in a way mimics the influence of the cosmological constant. It also appears that the dark energy enlarges the age of the universe which is demanded in cosmology. Finally, we propose to check for dark radiation and brane tension by the application of the angular diameter of galaxies minimum value test. The idea of brane universes has originated from Hořava and Witten [1] followed by Randall and Sundrum [2]. Brane models admit new parameters which are not present in standard cosmology (brane tension λ and dark radiation U). From the astronomical observations of supernovae Ia [3, 4] one knows that the universe is now accelerating and the best-fit model is for the 4-dimensional cosmological constant density parameter Ω Λ (4) ,0 = 0.72 and for the dust density parameter Ω m,0 = 0.28 (index "0" refers to the present moment of time). In other words, only the exotic (negative pressure) matter in standard cosmology can lead to this global effect. On the other hand, in brane models the ̺ 2 quadratic contribution in the energy density even for a small negative pressure, contributes effectively as the positive pressure, and makes brane models less accelerating. In this paper we argue that in order to avoid this problem

Observational Constraints on Cosmology from the Modified Friedmann Equation

“…We perform a combined analysis of data including the dimensionless coordinate distances to type Ia supernovae (SNeIa) and Fanaroff-Riley type IIb (FRIIb) radio galaxies compiled by Daly and Djorgovski (2003) and the X-ray gas mass fraction in clusters of galaxies published by Allen et al (2002Allen et al ( ,2003. These results are timely and complementary to the previous constraints from the angular size of high-z compact radio sources (Zhu and Fujimoto 2002), CMBR (Sen and Sen 2003a,b), the SNeIa database (Zhu and Fujimoto 2003a;Wang et al 2003;Cao 2003;Szydlowski and Czaja 2003;Godlowski and Szydlowski 2003), large scale structures (Multamaki et al 2003) and from optical gravitational lensing surveys .…”

Dark Matter and Dark Energy as Effects of Modified Gravity

“…Information criteria for model selection [29] can be used, in some subclass of dark energy models, in order to overcome this degeneracy [30,31]. Most popular are the Akaike information criteria (AIC) [33] and the Bayesian information criteria (BIC) [34].…”

Constraints on the Cardassian Scenario from the Expansion Turnaround Redshift and the Sunyaev‐Zeldovich/X‐Ray Data

“…The second term, called Cardassion term, 3 would drives the universe accelerating at a late epoch when it is dominated (or before or after it is dominated, which depends on the power index n being equal to or less or larger than 1/3, see section 3 for more detail discussion), without seeking to another unknown dark energy component. Several authors have explored the agreement of the Cardassian expansion model with various observations such as the compact radio source angular size versus redshift data (Zhu and Fujimoto 2002), the cosmic macrowave background anisotropy measurements Sen 2003a, 2003b), the distant type Ia supernovae data (Zhu and Fujimoto 2003;Wang et al 2003;Cao 2003;Szydlowski and Czaja 2003;Godlowski and Szydlowski 2003), optical gravitational lensing surveys (Dev, Alcaniz and Jain 2003b) and structure formation (Multamaki et al 2003).…”