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 and Type Ia supernovae. However, recent cosmological observations, particularly from DESI DR2, have renewed interest in possible departures from the cosmological constant. In this talk, I will first discuss the physics of progenitor age bias in Type Ia supernovae, motivated by the results of Project YONSEI, which provide evidence for a dependence of standardized SNe~Ia luminosities on progenitor age and host-galaxy properties. I will then discuss the cosmological implications of incorporating this progenitor age-bias correction into the analysis of different SNe~Ia samples combined with DESI DR2 and CMB observations. Without the age-bias correction, the preference for dynamical dark energy over $\Lambda$CDM ranges from approximately $2.0\sigma+$ to $3.0\sigma+$, depending on the SNe~Ia sample. Remarkably, after applying the age-bias correction, this preference increases substantially, reaching approximately $7\sigma+$--$11\sigma+$. The preferred dark energy evolution shows Quintom-B behavior, characterized by $w_0>-1$, $w_a<0$, and $w_0+w_a<-1$. I will also discuss the resulting evidence for phantom-crossing behavior in the evolution of dark energy. Finally, I will discuss the broader cosmological consequences of the age-bias correction, with particular emphasis on the $H_0$ tension. I will show how current cosmological observations constrain possible solutions to the $H_0$ tension and why the tension becomes increasingly difficult to resolve within the dark energy scenarios favored by DESI DR2 and the age-bias-corrected SNe~Ia data.
| Topic | The Hubble tension: observational results and possible solutions |
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