The bispectrum of relativistic galaxy number counts

Understand

We discuss the dominant terms of the relativistic galaxy number counts to second order in cosmological perturbation theory on sub-Hubble scales and on intermediate to large redshifts.

• In particular, we determine their contribution to the bispectrum.
• In addition to the terms already known from Newtonian second order perturbation theory, we find that there are a series of additional `lensing-like' terms which contribute to the bispectrum.
• We derive analytical expressions for the full leading order bispectrum and we evaluate it numerically for different configurations, indicating how they can be measured with upcoming surveys.