The unequal-time matter power spectrum: impact on weak lensing observables

Understand

We investigate the impact of a common approximation on weak lensing power spectra: the use of single-epoch matter power spectra in integrals over redshift.

• We disentangle this from the closely connected Limber's approximation.
• We derive the unequal-time matter power spectrum at one-loop in standard perturbation theory and effective field theory to deal with non-linear physics.
• We compare these formalisms and conclude that the unequal-time power spectrum using effective field theory breaks for larger scales.