Dynamical Dark Energy in light of the DESI DR2 Baryonic Acoustic Oscillations Measurements
Gan Gu, Xiaoma Wang, Yuting Wang, Gong-Bo Zhao, Levon Pogosian, Kazuya Koyama, John A. Peacock, Zheng Cai, Jorge L. Cervantes-Cota, Mustapha Ishak, Arman Shafieloo, Ruiyang Zhao, Steven Ahlen, Davide Bianchi, David Brooks, Todd Claybaugh, Shaun Cole, Axel de la Macorra, Arnaud de Mattia, Peter Doel, Simone Ferraro, Jaime E. Forero-Romero, Enrique Gaztañaga, Satya Gontcho A Gontcho, Gaston Gutierrez, ChangHoon Hahn, Cullan Howlett, Robert Kehoe, David Kirkby, Jean-Paul Kneib, Anthony Kremin, Ofer Lahav, Martin Landriau, Laurent Le Guillou, Alexie Leauthaud, Michael Levi, Marc Manera, Aaron Meisner, Ramon Miquel, John Moustakas, Andrea Muñoz-Gutiérrez, Seshadri Nadathur, Jeffrey A. Newman, Nathalie Palanque-Delabrouille, Will Percival, Francisco Prada, Ignasi Pérez-Ràfols, Graziano Rossi, Lado Samushia, Eusebio Sanchez, David Schlegel, Hee-Jong Seo, David Sprayberry, Gregory Tarlé, Michael Walther, Benjamin Alan Weaver, Pauline Zarrouk, Cheng Zhao, Rongpu Zhou, Hu Zou
Published: 2025/4/8
Abstract
Understanding whether cosmic acceleration arises from a cosmological constant or a dynamical component is a central goal of cosmology, and the Dark Energy Spectroscopic Instrument (DESI) enables stringent tests with high-precision distance measurements. We analyze baryon acoustic oscillation (BAO) measurements from DESI Data Release 1 (DR1) and Data Release 2 (DR2), combined with Type Ia supernovae and a cosmic microwave background (CMB) distance prior. With the larger statistical power and wider redshift coverage of DR2, the preference for dynamical dark energy does not diminish relative to DR1. Using both a shape-function reconstruction and non-parametric approaches with a Horndeski-motivated correlation prior, we find that the dark-energy equation of state $w(z)$ varies with redshift. BAO data alone yield modest constraints, but in combination with independent supernova compilations and the CMB prior they strengthen the evidence for dynamics. Bayesian model comparison shows moderate support for departures from $\Lambda$CDM when multiple degrees of freedom in $w(z)$ are allowed, corresponding to $\approx3\sigma$ tension with $\Lambda$CDM (and higher for some data sets). Despite methodological differences, our results are consistent with companion DESI papers, underscoring the complementarity of approaches. Possible systematics remain under study; forthcoming DESI, \emph{Euclid}, and next-generation CMB data will provide decisive tests.