Probing departures from $Λ$CDM by late-time datasets

Abstract: Observational data play a pivotal role in identifying cosmological models that are both theoretically consistent and empirically viable. In this work, we investigate whether the standard $\Lambda$CDM model exhibits significant departure with current late time datasets, including Cosmic Chronometers, Baryon Acoustic Oscillations from DESI DR2, and various Type Ia supernova compilations (Pantheon$^+$, DES-SN5Y, Union3). We analyze several dynamical dark energy models, including $\omega$CDM, o$\omega$CDM, $\omega_0\omega_a$CDM, Logarithmic, Exponential, JBP, BA, and GEDE. While CC + DESI DR2 data show mild deviations from $\Lambda$CDM ($\lesssim 2\sigma$), adding supernova samples (DES-SN5Y or Union3) increases deviations, with BA, JBP, and Logarithmic models reaching $3-3.5\sigma$, and CC + DESI DR2 + DES-SN5Y producing the largest deviations. We find consistent evidence for $\omega_0 > -1$ and $\omega_a < 0$ in all dark energy models, indicating that the cosmological constant faces a potential crisis and that dynamical dark energy models could provide a possible solution, characterized by a Quintom-B type scenario. The $\Lambda$CDM model has long served as the cornerstone of modern cosmology, successfully shaping our understanding of the Universe from its earliest epochs to the present day. However, in light of DESI DR2 and other recent measurements, emerging cracks in this paradigm suggest that a complete understanding of the cosmos may require moving beyond the cosmological constant and exploring new physics governing the dark sector.