CCA Colloquium: Neal Dalal

Title: AGN HBT OMG

Abstract: I’ll discuss an old technique called intensity interferometry, pioneered by Hanbury Brown and Twiss (HBT) that allows us to achieve sub-microarcsecond angular resolution using ordinary ground-based optical telescopes observing visible light. This technique is best suited for compact, bright sources, and I will discuss applications of intensity interferometry observations of bright, supermassive black holes called active galactic nuclei (AGN). I’ll describe a few possible applications, like measuring the Hubble constant H0 and probing the innermost structure of AGN accretion disks.

November 7, 2025