Is the $Λ$CDM Model in Crisis?

Himanshu Chaudhary; Salvatore Capozziello; Subhrat Praharaj; Shibesh Kumar Jas Pacif; G. Mustafa

doi:10.1016/j.jheap.2025.100507

paper

Is the $Λ$ CDM Model in Crisis?

arXiv:2509.17124 · doi:10.1016/j.jheap.2025.100507

Abstract

We present strong evidence for dynamical dark energy that challenges the standard $Λ$ CDM model. Several dark energy scenarios are explored, including $ω_{0} ω_{a}$ CDM, logarithmic, exponential, JBP, and BA parameterizations, along with non-flat cosmologies allowing for spatial curvature ( $Ω_{k} \neq = 0$ ). Our analysis supports a flat Universe with $Ω_{k} \approx 0$ . Using MCMC techniques, we constrain these models with observational data from DESI~DR2 baryon acoustic oscillations, Type~Ia supernovae, and compressed CMB likelihoods. The results provide strong statistical evidence that $ω \neq = - 1$ , favoring dynamical dark-energy behavior consistent with a Quintom-B scenario ( $ω_{0} > - 1$ , $ω_{a} < 0$ , and $ω_{0} + ω_{a} < - 1$ ). We also derive upper bounds on the total neutrino mass, $\sum m_{ν}$ , using CMB + DESI~DR2 data: $\sum m_{ν} < 0.066 eV$ for $Λ$ CDM and $\sum m_{ν} < 0.075 eV$ for $ω$ CDM. In the non-flat extensions, o $Λ$ CDM and o $ω$ CDM, the limits relax to $\sum m_{ν} < 0.263 eV$ and $\sum m_{ν} < 0.520 eV$ , respectively. For the other models $ω_{0} ω_{a}$ CDM, logarithmic, exponential, JBP, BA, and GEDE the constraints range between $< 0.043$ and $< 0.127 eV$ . The effective number of relativistic species remains consistent with the standard value, $N_{eff} = 3.044$ , across all models. Bayesian evidence further shows that combining DES-SN5Y or Union3 supernova samples with CMB + DESI~DR2 produces measurable deviations from $Λ$ CDM. Although no model reaches the $5 σ$ significance threshold, several exhibit tensions exceeding $3 σ$ , suggesting emerging cracks in the cosmological constant paradigm.

arXiv comment23 pages, 11 figures, Published in Journal of High Energy Astrophysics

Is the ΛCDM Model in Crisis?

Abstract

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Is the $Λ$ CDM Model in Crisis?