The Hubble tension and the early Universe

UBC Physics & Astronomy Department Colloquium on October 21, 2021. Presented by Marc Kamionkowski (Johns Hopkins).
phas.ubc.ca/hubble-tension-an...
The value of the cosmic expansion rate (the Hubble constant) inferred from observations of supernovae disagree with those inferred from measurements of the cosmic microwave background. Easy explanations for this discrepancy have been elusive, but the past few years attention has turned to the possibility that a modification to early-Universe physics may be required. I will discuss a solution to this "Hubble tension" that involves the introduction of a new component of matter, “early dark energy,” as well as other related ideas.