Trans-Planckian relics in the scalar to tensor ratio

TL;DR

This paper investigates how trans-Planckian physics and symmetry breaking at tiny scales during inflation can modify the primordial scalar to tensor ratio and power spectra, impacting cosmological predictions.

Contribution

It introduces models of trans-Planckian effects and symmetry breaking that alter the standard inflationary predictions for primordial fluctuations.

Findings

Trans-Planckian effects can shift the scalar to tensor ratio.

Modulations grow at smaller scales, affecting the ratio's scale dependence.

Symmetry breaking at horizon scales can suppress large-scale power.

Abstract

The physical properties of our universe at energy scales above the expansion rate during inflation can affect predictions for the ratio between the amplitudes of the primordial scalar and tensor fluctuations. In particular, we study here the effects of a breakdown of a locally Lorentz invariant description of nature at tiny space-time intervals. In some instances, these effects shift the amplitudes by a constant amount, altering the standard relation between this ratio and the slow-roll parameters. More generally, "trans-Planckian" effects introduce a modulation in the primordial power spectra which grows at shorter scales, making the value of the ratio sensitive to the scale at which it is defined. We also present a model where symmetries are broken at horizon scales during inflation. In this case, the power at large scales today could then be suppressed, relative to that at smaller scales.