Exploring new physics in the late Universe’s expansion through non-parametric inference

Miguel A. Sabogal; Özgür Akarsu; Alexander Bonilla; Eleonora Di Valentino; Rafael C. Nunes

doi:10.1140/epjc/s10052-024-13081-1

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2024) 84: 703
https://doi.org/10.1140/epjc/s10052-024-13081-1

Regular Article - Theoretical Physics

Exploring new physics in the late Universe’s expansion through non-parametric inference

Miguel A. Sabogal¹^a, Özgür Akarsu², Alexander Bonilla³, Eleonora Di Valentino⁴ and Rafael C. Nunes¹^,5

¹ Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre, RS, Brazil
² Department of Physics, Istanbul Technical University, Maslak, 34469, Istanbul, Turkey
³ Observatório Nacional, Rua General José Cristino 77, São Cristóvão, 20921-400, Rio de Janeiro, RJ, Brazil
⁴ School of Mathematics and Statistics, University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK
⁵ Divisão de Astrofísica, Instituto Nacional de Pesquisas Espaciais, Avenida dos Astronautas 1758, São José dos Campos, 12227-010, São Paulo, Brazil

^a miguel.sabogal@ufrgs.br

Received: 26 January 2024
Accepted: 1 July 2024
Published online: 16 July 2024

Abstract

In this study, we investigate deviations from the Planck- $Λ$ $\Lambda$ CDM model in the late universe ( $z ≲ 2.5$ $z \lesssim 2.5$ ) using the Gaussian Processes method, with minimal assumptions. Our goal is to understand where exploring new physics in the late universe is most relevant. We analyze recent Cosmic Chronometers (CC), Type Ia Supernovae (SN), and Baryon Acoustic Oscillations (BAO) data. By examining reconstructions of the dimensionless parameter $δ (z)$ $\delta (z)$ , which measures deviations of the Hubble parameter from the Planck- $Λ$ $\Lambda$ CDM predictions, we identify intriguing features at low ( $z ≲ 0.5$ $z \lesssim 0.5$ ) and high ( $z ≳ 2$ $z \gtrsim 2$ ) redshifts. Deviations from the Planck- $Λ$ $\Lambda$ CDM model were not significant between $0.5 ≲ z ≲ 2$ $0.5\lesssim z \lesssim 2$ . Using the combined CC+SN+BAO dataset, we gain insights into dark energy (DE) dynamics, resembling characteristics of omnipotent DE, extending beyond quintessence and phantom models. DE exhibits n-quintessence traits for $z ≳ 2$ $z\gtrsim 2$ , transitioning with a singularity around $z \sim 2$ $z\sim 2$ to usual phantom traits in $1 ≲ z ≲ 2$ $1\lesssim z\lesssim 2$ . DE characteristics differ between scenarios ( $H_{0}$ $$H_0$$ -SH0ES and $H_{0}$ $$H_0$$ - $Λ$ $\Lambda$ &CMB), with $H_{0}$ $$H_0$$ -SH0ES leaning towards phantom traits and $H_{0}$ $$H_0$$ - $Λ$ $\Lambda$ &CMB towards quintessence. We suggest exploring new physics at $z ≲ 0.5$ $z\lesssim 0.5$ and $1.5 ≲ z ≲ 2.5$ $1.5\lesssim z\lesssim 2.5$ , particularly around $z = 2$ $$z = 2$$ , to understand cosmological tensions such as $H_{0}$ $$H_0$$ and $S_{8}$ $$S_8$$ .

© The Author(s) 2024

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