Cosmic slowing down of acceleration with the Chaplygin-Jacobi gas as a dark fluid?

TL;DR

This paper introduces a generalized Chaplygin-Jacobi dark fluid model that predicts a transient acceleration phase in the universe, contrasting with the eternal acceleration of standard models, and tests its observational viability.

Contribution

The paper develops a novel Chaplygin-Jacobi model using elliptic functions and Hamilton-Jacobi formalism, exploring its implications for cosmic acceleration and comparing it with observational data.

Findings

Supports transient acceleration with current data

Strongly disfavored compared to ΛCDM

Differs from standard Chaplygin gas models

Abstract

A particular generalization of the Chaplygin inflationary model, using the formalism of Hamilton-Jacobi and elliptic functions, results in a more general non-linear Chaplygin-type equation of state (Chaplygin-Jacobi model). We investigate the implementation of this model as a dark energy (DE) fluid to explain the recent acceleration of the universe. Unlike $\Lambda$CDM and other Chaplygin-like fluids, where the final fate of the universe is an eternal de Sitter (dS) phase, the dynamics of this model allows for the possibility of a decelerating phase in the future, following the current accelerating phase. In other words, a transient acceleration arises, accounting for the recently claimed slowing down phenomenon. This Chaplygin-Jacobi model shows important differences compared to the standard and generalized Chaplygin gas models. Additionally, we perform a Markov Chain Monte Carlo (MCMC) analysis using several datasets, including Type Ia Supernovae (SNIa), Cosmic Chronometers (CC), Fast Radio Bursts (FRBs), and Baryon Acoustic Oscillations (BAO) to examine the observational viability of the model. Our results indicate that, although a transient phase of accelerated expansion is supported by current observations in the context of the Chaplygin-Jacobi model, this model is strongly disfavored in comparison with $\Lambda$CDM.