Speaker
Description
The $\Lambda$CDM model has long been regarded as the standard paradigm of modern cosmology, providing an excellent description of the Universe across a wide range of observations, from the cosmic microwave background to large-scale structure formation and Type Ia supernovae. The discovery of the accelerated expansion of the Universe further established dark energy as one of the central components of the cosmological model. In this talk, I will show that the preference for a dynamical dark energy model over $\Lambda$CDM ranges from $2.0\sigma+$-$3.0\sigma+$, depending on which SNe Ia sample is combined with DESI DR2 and CMB observations. Interestingly, we find that the dark energy behavior preferred by DESI DR2 is characterized by the \textbf{Quintom-B} behavior ($w_0 > -1$, $w_a < 0$, and $w_0 + w_a < -1$). I will further discuss the implications of the \textbf{Project YONSEI} results, which provide evidence for luminosity evolution in Type Ia supernovae associated with progenitor age effects and host galaxy properties. We incorporate progenitor age-bias corrections into cosmological analyses and investigate their impact on dark energy constraints. Remarkably, after applying the age-bias correction, the dynamical dark energy model over $\Lambda$CDM ranges from $7\sigma+$--$11\sigma+$. I will also present evidence for phantom crossing behavior. Furthermore, I will discuss how the peak of the posterior distribution for $\sum m_{\nu}$ shifts toward the normal mass ordering when using the DESI DR2 + CMB + Union3 combination after applying the corrections. Finally, I will discuss the evidence for a non-accelerating Universe scenario after applying the age-bias correction, and show that the $H_0$ tension in dark after age-bias correction.