Current Understanding and Recent Work on Cosmology, Galaxy Formation - Livestream

The modern standard cosmology ΛCDM describes almost perfectly the cosmic microwave background observations, but the resulting expansion rate of the universe (the Hubble parameter) is in serious disagreement with local measurements. This Hubble tension can be resolved by a brief episode of dark energy contributing about 10% of cosmic energy density at redshift z ~ 3500, about 30,000 years after the Big Bang. Our N-body simulations have shown that this “Early Dark Energy” (EDE) scenario predicts earlier structure formation, for example 50% more clusters than ΛCDM at redshift z∼1.

Galaxies were long thought to start as disks, but Hubble Space Telescope images show that most galaxies instead start prolate (pickle shaped). Galaxy simulations can explain this as a consequence of the filamentary nature of the ΛCDM dark matter distribution. But our comparisons between simulations and observations using novel machine learning methods have revealed other potential challenges, for example the giant clumps that are ubiquitous in z >1 star-forming galaxies

Speaker: Dr. Joel Primack, UC Santa Cruz

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