18 December 2024: Hassan Amirhashchi

Speaker: Hassan Amirhashchi

Date: Wednesday 18 December 2024

Time: 15:00

Location: Physics 3.21

Hubble Tension: A kinematic View Beyond The Standard Model

Cosmography is a framework used to describe the kinematics of the universe without assuming a specific cosmological model. Instead, it relies on observational data, such as the expansion rate of the universe, to build a model-independent description. This approach is particularly useful in studying phenomena like dark energy and the Hubble tension, where the underlying physics is not fully understood. The cornerstone of cosmography is to expand some observables such as the Hubble parameter (or equivalently the scale factor) into power series, and directly relating cosmological parameters to these observable quantities. The cosmographic approach can help identify whether the observed acceleration is due to a cosmological constant (as in ΛCDM) or if it suggests more complex dynamics, such as evolving dark energy or modifications to general relativity. In other hand, cosmography provides a valuable tool for investigating the Hubble tension by offering a model-independent way to reconstruct the expansion history of the universe. By comparing the cosmographic parameters obtained from different observational datasets, cosmologists can identify inconsistencies and potential sources of the Hubble tension. Some cosmologists have proposed that the Hubble tension might be resolved by introducing new physics, such as early dark energy or interactions between dark energy and dark matter. Cosmography allows these hypotheses to be tested without committing to specific models, providing a flexible framework for exploring potential solutions.