David Marsh, The String Axiverse in 2023

ITMP seminar, May 24, 2023
Speaker: Dr. David Marsh, King's College London
Title: The String Axiverse in 2023
Abstract: In 2009 the highly influential idea of a "string axiverse" was proposed, which has dominated my own research. This talk attempts to review the progress myself and others have made on this idea in the last 14 years. The original probes proposed: matter power spectrum, birefringence, superradiance, and axion decays have all matured in precision both theoretically and observationally, which I will describe, along with other related probes, in particular in cosmology. I will then describe recent dramatic progress that has been made in constructing explicit axiverses from Calabi-Yau compactifications across the entire "Kreuzer-Skarke" database in Type IIB string theory, and the similarities and differences between such axiverses and the conjectures in 2009. Superradiance has already been used to constrain the resulting landscape in a narrow search. I will end by outlining some dreams for the future of this program.