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

J. A. S. Fortunato; W. S. Hipólito-Ricaldi; N. Videla; J. R. Villanueva

doi:10.1140/epjc/s10052-025-13996-3

2023 Impact factor 4.2

Particles and Fields

Open Access

Eur. Phys. J. C (2025) 85: 274
https://doi.org/10.1140/epjc/s10052-025-13996-3

Regular Article - Theoretical Physics

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

J. A. S. Fortunato¹^,2^,3, W. S. Hipólito-Ricaldi²^,4, N. Videla⁵^a and J. R. Villanueva⁶

¹ PPGCosmo, CCE, Universidade Federal do Espírito Santo, Av. Fernando Ferrari, 540, CEP 29.075-910, Vitória, ES, Brazil
² Núcleo Cosmo-UFES, CCE, Universidade Federal do Espírito Santo, Av. Fernando Ferrari, 540, CEP 29.075-910, Vitória, ES, Brazil
³ Instituto Argentino de Radioastronomía, C.C. No. 5, 1894, Buenos Aires, Argentina
⁴ Departamento de Ciências Naturais, CEUNES, Universidade Federal do Espírito Santo, Rodovia BR 101 Norte, km. 60, CEP 29.932-540, São Mateus, ES, Brazil
⁵ Instituto de Física, Pontificia Universidad Católica de Valparaíso, Avenida Universidad 331, Curauma, Valparaiso, Chile
⁶ Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Avenida Gran Bretaña 1111, Playa Ancha, Valparaiso, Chile

^a nelson.videla@pucv.cl

Received: 1 October 2024
Accepted: 22 February 2025
Published online: 12 March 2025

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 $Λ$ $\Lambda$ 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 $Λ$ $\Lambda$ CDM.

© The Author(s) 2025

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