Uniqueness of Current Cosmic Acceleration

TL;DR

This paper investigates the rarity of cosmic acceleration episodes, especially between recombination and recent times, by constraining their duration to avoid significant alterations in the matter power spectrum.

Contribution

It provides new limits on the duration of intermediate acceleration epochs, challenging the notion of multiple acceleration phases in cosmic history.

Findings

Acceleration epochs longer than 0.05 e-folds are inconsistent with observed matter power spectrum

The likelihood of multiple acceleration episodes is highly constrained by cosmological data

Current data limits the duration of any intermediate acceleration to preserve structure formation

Abstract

One of the strongest arguments against the cosmological constant as an explanation of the current epoch of accelerated cosmic expansion is the existence of an earlier, dynamical acceleration, i.e. inflation. We examine the likelihood that acceleration is an occasional phenomenon, putting stringent limits on the length of any accelerating epoch between recombination and the recent acceleration; such an epoch must last less than 0.05 e-fold (at z>2) or the matter power spectrum is modified by more than 20%.