Research Seminars @ Illinois

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Tailored for undergraduate researchers, this calendar is a curated list of research seminars at the University of Illinois. Explore the diverse world of research and expand your knowledge through engaging sessions designed to inspire and enlighten.

To have your events added or removed from this calendar, please contact OUR at ugresearch@illinois.edu

High Energy Physics Seminar - Qianshu Lu (Institute for Advanced Study) - "The Quality/Cosmology Tension for a Post-Inflation QCD Axion"

Event Type: Seminar/Symposium
Sponsor: Department of Physics
Location: Room 464
Date: Nov 22, 2024 11:00 am
Speaker: Qianshu Lu (Institute for Advanced Study)
Contact: Brandy Koebbe
E-Mail: BKOEBBE@ILLINOIS.EDU
Views: 21
Originating Calendar: Physics - High Energy Physics Seminar; The QCD axion is not only a leading contender as a solution to the Strong CP problem, it is also a natural dark matter candidate. In particular, the post-inflationary axion has been claimed to produce a unique prediction of the axion mass if axion makes up all of dark matter. On the other hand, QCD axion models often suffers from the so-called axion quality problem, where the axion shift symmetry is unprotected from quantum gravity effects. In this talk I will discuss the tension between solutions to the quality problem and viable cosmology for post-inflationary QCD axions. I will start with a simple Z_N solution as an illustrative example of the close connection between the quality problem and the domain wall problem. I will then analyze proposals in the literature that involve more complex symmetry structure and show that they share a set of cosmological issues, including the domain wall problem and fractionally charged particles. Our study suggests that a viable post-inflationary QCD axion model is likely to have non-standard cosmological history unlike what is being assumed in recent simulations, and the “correct” axion mass to produce all of dark matter is far from certain.

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