Testing Gravity Using Type Ia Supernovae Discovered by Next-Generation Wide-Field Imaging Surveys.

In the upcoming decade cadenced wide-field imaging surveys will increase thenumber of identified $zu003c0.3$ Type~Ia supernovae (SNe~Ia) from the hundreds tothe hundreds of thousands. The increase in the number density and solid-anglecoverage of SNe~Ia, in parallel with improvements in the standardization oftheir absolute magnitudes, now make them competitive probes of the growth ofstructure and hence of gravity. The peculiar velocity power spectrum issensitive to the growth index $gamma$, which captures the effect of gravity onthe linear growth of structure through the relation $f=Omega_M^gamma$. Wepresent the first projections for the precision in $gamma$ for a range ofrealistic SN peculiar-velocity survey scenarios. In the next decade thepeculiar velocities of SNe~Ia in the local $zu003c0.3$ Universe will provide ameasure of $gamma$ to $pm 0.01$ precision that can definitively distinguishbetween General Relativity and leading models of alternative gravity.