Can We Avoid Dark Energy?

The idea that we live near the center of a large, nonlinear void has attracted attention recently as an alternative to dark energy or modified gravity. We show that an appropriate void profile can fit both the latest cosmic microwave background and supernova data. However, this requires either a fine-tuned primordial spectrum or a Hubble rate so low as to rule these models out. We also show that measurements of the radial baryon acoustic scale can provide very strong constraints. Our results present a serious challenge to void models of acceleration.

Figure 1

Local density parameter ${\Omega }_m^{\mathrm{loc}}$ versus redshift $z$ for constrained (left) and unconstrained (right) voids. The profiles are sampled from MCMC chains and the gray scale level indicates the relative likelihood.

Figure 2

Likelihood contours at 68% and 95% confidence for constrained (blue, solid contours) and unconstrained (red, dashed contours) voids.

Figure 3

Residual $C_{\ell }$’s (in $\mu {\mathrm{K}}^2$) from the best-fit $\Lambda$ model for constrained (top) and unconstrained (bottom) voids. Binned WMAP data are shown by the red (thick) error bars, and ACBAR data by the blue (thin) bars.

Figure 4

RBAO scale $\Delta z^{\mathrm{BAO}}$ for constrained (left) and unconstrained (right) voids. Also shown are the RBAO data from 33 (error bars), best-fit $\Lambda$ model (blue, dashed), and best-fit void including RBAO constraints (green, dot-dashed).