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Supernova limits on brane world cosmology

Malcolm Fairbairn, Ariel Goobar

TL;DR

The paper tests brane-world gravity, specifically the DGP model, as an alternative to dark energy by using SNLS Type Ia supernovae and a baryon acoustic oscillation prior from SDSS. The DGP Friedmann equation introduces a crossover scale $r_c$ and a density parameter $\Omega_{r_c}$, leading to a flat-universe constraint $\Omega_M+\Omega_k+2\sqrt{\Omega_{r_c}}\sqrt{1-\Omega_k}=1$. With the combined data, the DGP scenario is incompatible with a spatially flat universe, and generalized models with an $H^{\alpha}$ term yield a best-fit around $\alpha\approx0$, corresponding to a cosmological constant–like behavior with $w\approx-1$. The results place tight constraints on brane-induced gravity as a mechanism for cosmic acceleration and suggest limited room for deviations from a standard dark-energy paradigm within these models.

Abstract

By combining the first year data from the Supernova Legacy Survey (SN LS) and the recent detection of the baryon acoustic peak in the Sloan Digital Sky Survey data, we are able to place strong constraints on models where the cosmic acceleration is due to the leakage of gravity from the brane into the bulk on large scales. In particular, we are able to show that the DGP model is not compatible with a spatially flat universe. We generalize our analysis to phenomenological toy models where the curvature of the brane enters into the Friedmann equations in different ways.

Supernova limits on brane world cosmology

TL;DR

The paper tests brane-world gravity, specifically the DGP model, as an alternative to dark energy by using SNLS Type Ia supernovae and a baryon acoustic oscillation prior from SDSS. The DGP Friedmann equation introduces a crossover scale and a density parameter , leading to a flat-universe constraint . With the combined data, the DGP scenario is incompatible with a spatially flat universe, and generalized models with an term yield a best-fit around , corresponding to a cosmological constant–like behavior with . The results place tight constraints on brane-induced gravity as a mechanism for cosmic acceleration and suggest limited room for deviations from a standard dark-energy paradigm within these models.

Abstract

By combining the first year data from the Supernova Legacy Survey (SN LS) and the recent detection of the baryon acoustic peak in the Sloan Digital Sky Survey data, we are able to place strong constraints on models where the cosmic acceleration is due to the leakage of gravity from the brane into the bulk on large scales. In particular, we are able to show that the DGP model is not compatible with a spatially flat universe. We generalize our analysis to phenomenological toy models where the curvature of the brane enters into the Friedmann equations in different ways.

Paper Structure

This paper contains 5 sections, 19 equations, 3 figures.

Table of Contents

  1. Introduction
  2. The DGP model
  3. Confronting the model with cosmological data
  4. Generalisations of the DGP model
  5. Conclusions

Figures (3)

  • Figure 1: The solid curves show the allowed parameter regions in the $\Omega_M -\Omega_{r_c}$ plane at the 68, 90 and 99% confidence level. Solid thin contours correspond to the the first year SNLS data in Astier et al (2005)astier05, the dashed lines show the corresponding regions from the baryon oscillation peak in Eisenstein et al (2005) Eisenstein05. The coloured contours indicate the result of the combination of both data-sets. The thick solid lines indicate the expected relation between $\Omega_M$ and $\Omega_{r_c}$ in a flat universe.
  • Figure 2: Allowed 68, 90 and 95 % confidence regions in the $w_0$,$w_1$ parameter space for the first year SNLS data with baryon oscillation prior in a flat universe. The linear expansion $w(z) = w_0 + w_1\cdot z$ has been assumed. The best fit solution $(w_0=-1.07,w_1=0.14)$ is also shown.
  • Figure 3: Allowed parameter regions in the $\alpha$--$\Omega_M$ plane at the 1 $\sigma$ (one parameter), 68, 90 and 95% confidence level for a flat universe.