$\Lambda$ is Coming: Parametrizing Freezing Fields

TL;DR

This paper introduces two parametrizations for freezing dark energy models, accurately fitting key cosmological observables and the equation of state, thus providing a practical tool for analyzing late-time cosmic acceleration.

Contribution

It proposes two new two-parameter models for freezing dark energy, inspired by flow parameters and phase space, improving the accuracy of cosmological predictions.

Findings

Distances and Hubble parameters fit within 0.1% of exact solutions

Dark energy equation of state predicted within 1% accuracy

Models effectively describe late-time cosmic acceleration

Abstract

We explore freezing dark energy, where the evolution of the field approaches that of a cosmological constant at late times. We propose two general, two parameter forms to describe the class of freezing field models, in analogy to ones for thawing fields, here based on the physics of the flow parameter or the calibrated $w$-$w'$ phase space. Observables such as distances and Hubble parameters are fit to within 0.1%, and the dark energy equation of state generally to within better than 1%, of the exact numerical solutions.