Searching for modified gravity with baryon oscillations: From SDSS to wide field multiobject spectroscopy (WFMOS)

We discuss how the baryon acoustic oscillation (BAO) signatures in the galaxypower spectrum can distinguish between modified gravity and the cosmologicalconstant as the source of cosmic acceleration. To this end we consider a modelcharacterized by a parameter $n$, which corresponds to theDvali-Gabadadze-Porrati (DGP) model if $n=2$ and reduces to the standardspatially flat cosmological constant concordance model for $n$ equal toinfinity. We find that the different expansion histories of the modifiedgravity models systematically shifts the peak positions of BAO. A preliminaryanalysis using the current SDSS LRG sample indicates that the original DGPmodel is disfavored unless the matter density parameter exceeds 0.3. Theconstraints will be strongly tightened with future spectroscopic samples ofgalaxies at high redshifts. We demonstrate that WFMOS, in collaboration withother surveys such as Planck, will powerfully constrain modified gravityalternatives to dark energy as the explanation of cosmic acceleration.Comment: Physical Review D, in pres