Ultraviolet-regularized power spectrum without infrared distortions in cosmological spacetimes

We reexamine the regularization of two-point function a scalar field in Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. Adiabatic provides set subtraction terms momentum space that successfully remove its ultraviolet divergences at coincident points, but can significantly distort power spectrum infrared scales, especially for light fields. In this work we propose, by using intrinsic ambiguities renormalization program, new minimize distortions scales $k \lesssim M$, with $M$ an arbitrary mass scale. Our method is consistent local covariance and equivalent to general methods curved apply our results de Sitter space: while adiabatic scheme yields exactly $\Delta_{\phi}^{\rm (reg)} = 0$ massless field, proposed prescription recovers standard scale-invariant result \simeq H^2 /(4\pi^2)$ super-horizon scales.