Cosmological Models Tested: New Approaches to Distance Measurements

Recent studies in cosmology have focused on refining models to enhance our understanding of distance measurements across the universe, particularly addressing discrepancies in the Hubble constant. A notable contribution comes from a study titled 'A Case for an Inhomogeneous Einstein-de Sitter Universe', which proposes that cosmic acceleration can be explained through local dynamics in an inhomogeneous Einstein-de Sitter universe, without the need for dark energy.

This model indicates a quasilinear evolution towards a Milne state driven by growing inhomogeneities, which could lead to effective negative curvature while maintaining spatial flatness. The study tested two realizations of the inhomogeneous universe, iEdS(1) and iEdS(2), with Hubble constant values of 70.24 and 74.00 kilometers per second per megaparsec, respectively.

Notably, iEdS(1) fits observational data better than the standard Lambda Cold Dark Matter model, alleviating the Hubble tension, while iEdS(2) fully resolves it, consistent with the age estimates of globular clusters at approximately 13.64 billion years.

Additionally, another study titled 'Cosmological Impacts of Black Hole Mergers: No Relief in Sight for the Hubble Tension' highlights the ongoing tension between local measurements and cosmic microwave background observations of the Hubble constant, suggesting that black hole mergers cannot mitigate this discrepancy.

The research indicates that converting matter to gravitational radiation through black hole mergers, whether from supermassive black holes or stellar-mass black holes, is insufficient to resolve the Hubble tension, requiring unrealistic merger rates or an overproduction of supermassive black holes.

Thus, while innovative approaches to cosmological models are being explored, significant challenges remain in reconciling the observed values of the Hubble constant and understanding the expansion of the universe.