Speaker
Description
The standard Lambda–Cold–Dark–Matter (LambdaCDM) cosmological model has been remarkably successful in describing the large-scale Universe, yet it faces growing challenges from observations, including the persistent Hubble tension, emerging evidence of evolving dark energy, and the unexpectedly abundant population of massive galaxies discovered by JWST at redshift z>10. These observations collectively suggest that the LambdaCDM may be incomplete, motivating physically motivated extensions to the current model.
I will present Harmonic Axion Unified Cosmology (HAUC), a multi-axion model in which axion-like fields spanning different mass scales naturally generate the universe’s fundamental components. In this framework, an ultra-light axion drives a time-evolving dark-energy density, a light axion produced via the misalignment mechanism forms wave-like dark matter, and overdensities of heavy axions during inflation produce primordial black holes. Using cosmological simulations incorporating the HAUC model, we find that primordial black holes provide early gravitational seeds that accelerate the formation of the first galaxies and supermassive black holes. The results suggest that the HAUC framework can naturally enhance early structure formation while remaining broadly consistent with current cosmological constraints. I will discuss the physical mechanisms of the model, simulation results, and observational tests with current and upcoming multi-band surveys of galaxies and black holes at the cosmic dawn.
| Research Area | Cosmology: late universe |
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