Short distance signatures in Cosmology: Why not in Black Holes?

TL;DR

This paper investigates why short distance physics signatures are observable in cosmology but not in black hole radiation, using moving mirror models to compare their responses and implications for quantum fluctuations.

Contribution

It provides a detailed analysis of the differing sensitivities of cosmological and black hole spectra to short distance physics using a moving mirror toy model.

Findings

Cosmological spectra retain signatures of short distance physics.

Black hole radiation signatures are suppressed due to averaging over quantum fluctuations.

The sensitivity differences are explained through a new averaging prescription.

Abstract

Current theoretical investigations seem to indicate the possibility of observing signatures of short distance physics in the Cosmic Microwave Background spectrum. We try to gain a deeper understanding on why all information about this regime is lost in the case of Black Hole radiation but not necessarily so in a cosmological setting by using the moving mirror as a toy model for both backgrounds. The different responses of the Hawking and Cosmic Microwave Background spectra to short distance physics are derived in the appropriate limit when the moving mirror mimics a Black Hole background or an expanding universe. The different sensitivities to new physics, displayed by both backgrounds, are clarified through an averaging prescription that accounts for the intrinsic uncertainty in their quantum fluctuations. We then proceed to interpret the physical significance of our findings for time-dependent backgrounds in the light of nonlocal string theory.