A Note on Trans-Planckian Tail Effects

TL;DR

This paper investigates whether tail modes with a specific dispersion relation can account for dark energy through their back-reaction, finding they produce an effective positive cosmological constant.

Contribution

It introduces a model where tail modes with exponential decay in the trans-Planckian regime induce a dark energy-like effect via their back-reaction on spacetime.

Findings

Tail modes induce a positive cosmological constant-like equation of state.

Matter perturbations dominate over metric fluctuations in this model.

The model supports the idea that trans-Planckian physics can influence cosmic acceleration.

Abstract

We study the proposal by Mersini et al. that the observed dark energy might be explained by the back-reaction of the set of tail modes in a theory with a dispersion relation in which the mode frequency decays exponentially in the trans-Planckian regime. The matter tail modes are frozen out, however they induce metric fluctuations. The energy-momentum tensor with which the tail modes effect the background geometry obtains contributions from both metric and matter fluctuations. We calculate the equation of state induced by the tail modes taking into account the gravitational contribution. We find that, in contrast to the case of frozen super-Hubble cosmological fluctuations, in this case the matter perturbations dominate, and they yield an equation of state which to leading order takes the form of a positive cosmological constant.