The Little Rip

TL;DR

This paper explores models of dark energy where the density increases over time without causing a future singularity, leading to a 'little rip' that can destroy bound structures without a big rip scenario.

Contribution

It refines conditions for 'little rip' models and compares their observational signatures to big rip models, highlighting differences in structure disintegration timing.

Findings

Little rip models can cause bound structures to disintegrate without a future singularity.

For the same current w, big rip disintegrates structures earlier than little rip.

Observational constraints can distinguish between little rip and big rip scenarios.

Abstract

We examine models in which the dark energy density increases with time (so that the equation-of-state parameter w satisfies w < -1), but w approaches -1 asymptotically, such that there is no future singularity. We refine previous calculations to determine the conditions necessary to produce this evolution. Such models can display arbitrarily rapid expansion in the near future, leading to the destruction of all bound structures (a "little rip"). We determine observational constraints on these models and calculate the point at which the disintegration of bound structures occurs. For the same present-day value of w, a big rip with constant w disintegrates bound structures earlier than a little rip.