Speaker: Prof. Gary Shiu (University of Wisconsin at Madison)

Time: 10:30AM, Sep. 29th (Tuesday)

Place: Theoretical Physics Division，319

Abstract:

Axion-like fields enjoy a shift symmetry that can only be broken by non-perturbative effects. Depending on the axion decay constant which defines the axion periodicity, axion-like particles can be candidates for dark matter and inflation. In this talk, we discussed how quantum gravity can constrain the axion field range. The constraint has implications on axion inflation, which requires super-Planckian field excursion. We show how multi-axion systems, regardless of their kinetic mixings and alignment, are constrained by general principles of quantum gravity.We will also critically address possible loopholes of this “no-go” theorem, attempts to overcome it, and attempts to embed axion inflation in string theory.