Work

One-parameter dynamical dark energy: Hints for oscillations

Year: 2026

Type: article

Abstract: There is mounting evidence from multiple cosmological probes that dark energy may be dynamical, with an equation of state that evolves over cosmic time. While this evidence is typically quantified using the Chevallier-Polarski-Linder (CPL) parametrization, based on a linear expansion of w ( a ) in the scale factor, nonparametric reconstructions frequently suggest nonlinear features, particularly at late times. In this work, we investigate four minimal one-parameter models of dark energy with nonlinear dependence on the scale factor. These models are constrained using cosmic microwave background data from , lensing reconstruction from and ACT-DR6, baryon acoustic oscillation measurements from DESI-DR2, and three type Ia supernovae (SNe) samples (PantheonPlus, DESY5, and Union3), considered independently. Although our conclusions depend on the choice of SNe sample, we consistently find a preference, as measured by the chi-squared statistic and the Bayesian evidence, for these dynamical dark energy models over the standard Λ CDM (cold dark matter) model. Notably, with the PantheonPlus dataset, one model shows strong Bayesian evidence ( Δ ln B ≃ 4.5 ) over CPL, favoring an equation of state that peaks near a ≃ 0.7 and oscillates near the present day. These results highlight the impact of SNe selection and contribute to the growing collection of evidence for late-time deviations from Λ CDM .

Source: Physical review. D/Physical review. D.

DOI: 10.1103/1x6w-4tnd

Authors: Daniel A. Kessler, Luis A. Escamilla, Supriya Pan, Eleonora Di Valentino

Institutions: University of Sheffield, Istanbul Technical University, Presidency University, Durban University of Technology, Presidency University

Language: English

Topic: Cosmology and Gravitation Theories

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid