Λ is Coming: Parametrizing Freezing Fields

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.