Galaxy Power Spectrum in General Relativity

Understand

We present the galaxy power spectrum in general relativity.

• Using a novel approach, we derive the galaxy power spectrum taking into account all the relativistic effects in observations.
• In particular, we show independently of survey geometry that relativistic effects yield no divergent terms (proportional to $k^{-4}P_m(k)$ or $k^{-2}P_m(k)$ on all scales) that would mimic the signal of primordial non-Gaussianity.
• This cancellation of such divergent terms is indeed expected from the equivalence principle, meaning that any perturbation acting as a uniform gravity on the scale of the experiment cannot be measured.