Speaker
Description
In the first part of this talk, I will review the Hubble tension and then describe some theoretical efforts to alleviate it---as well as the discrepancy with the BAO Lyman-α data — via the dark energy models that yield negative density values in the past. I will then discuss a recent work with two minimal extensions of the ΛCDM model, together or separately, can realize such a scenario: (i) The spatial curvature, which, in the case of spatially closed universe, mimics a negative density source, (ii) Simple-graduated dark energy, which promotes the null inertial mass density of the usual vacuum energy to an arbitrary constant — if negative, the corresponding energy density decreases with redshift similar to the phantom models, but unlike them crosses below zero at a certain redshift. I will close the talk by presenting the results when these are constrained using the latest observational data.
