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(02.11.) Glimmers from the Axiverse
Jakob Moritz (CERN)
02.11.2023 at 16:15
In this talk I will start by outlining why and how a class of pseudo-scalar particles called axions provide a promising experimental and observational window into the UV physics of string theory. Motivated by this I will present a new systematic study of axion-photon couplings in compactifications of type IIB string theory on Calabi-Yau threefolds, based on my recent paper 2309.13145 with Gendler, Marsh and McAllister. It will turn out that these couplings are systematically suppressed compared to the inverse axion periodicity, as a result of two effects. First, couplings to the QED theta angle are suppressed for axion mass eigenstates that are light compared to the mass scale set by stringy instantons on the cycle(s) supporting QED. Second, in compactifications with many axions the intersection matrix is sparse, making kinetic mixing weak. I will present results on the resulting phenomenology in an ensemble of 200,000 toy models constructed from the Kreuzer-Skarke database up to the maximum Hodge number $h^{1,1}=491$. These include an examination of freeze-in production and decay of thermal axions, birefringence of the cosmic microwave background, X-ray spectrum oscillations, and constraints on the QCD axion from supernovae. In conclusion, compactifications in this corner of the landscape involve many invisible axions, as well as a handful that may be detectable via photon couplings.
Arnold Sommerfeld Center Theresienstrasse 37
Room 348 via ZOOM