A Cosmic Model Parameterizing the late Universe

TL;DR

This paper proposes a simplified cosmological model that combines dark energy and curvature effects into one parameter, aiming to distinguish between different sources of cosmic acceleration and fit observational data.

Contribution

It introduces a new parameterization that reduces degeneracies and effectively separates curvature effects from dark energy in cosmological models.

Findings

Model is consistent with current cosmological observations.

Degeneracies between parameters are analyzed and visualized.

Effective dark energy equation of state is derived.

Abstract

A simple speed-up cosmology model is proposed to account for the dark energy puzzle. We condense contributions from dark energy and curvature term into one effective parameter in order to reduce parameter degeneracies and to find any deviation from flat concordance $\Lambda$CDM model, by considering that the discrimination between dynamical and non-dynamical sources of cosmic acceleration as the best starting point for analyzing dark energy data sets both at present and in future. We also combine recent Type Ia Supernova (SNIa), Cosmic Microwave Background (CMB) and Baryon Oscillation (BAO) to constrain model parameter space. Degeneracies between model parameters are discussed by using both degeneracy diagram and data analysis including high redshift information from Gamma Ray Bursts (GRBs) sample. The analysis results show that our model is consistent with cosmological observations. We try to distinct the curvature effects from the specially scaling dark energy component as parameterized. We study the linear growth of large scale structure, and finally show the effective dark energy equation of state in our model and how the matter component coincidences with the dark energy numerically.