Abstract

The seminar will take place via zoom: https://maths-cam-ac-uk.zoom.us/j/95215212460?pwd=TWN5cjJ3azErSUYremw5UWRKL0NKUT09

Abstract: We explore whether the axion which solves the strong CP problem can naturally be much lighter than the canonical QCD axion. The Z_N symmetry proposed by Hook, with N mirror and degenerate worlds coexisting in Nature and linked by the axion field, is considered. Two specific ultraviolet Z_N completions are developed: a composite axion one and a KSVZ -like model with improved Peccei-Quinn quality. On a second step, we show that dark matter can be accounted for by this extremely light axion. This includes the first proposal of a ``fuzzy dark matter’’ QCD axion. A novel misalignment mechanism occurs—trapped misalignment—due to the peculiar temperature dependence of the Z_N axion potential. The dark matter relic density is enhanced because the axion field undergoes two stages of oscillations: it is first trapped in the wrong minimum, which effectively delays the onset of true oscillations. Furthermore, the trapped misalignment can also dynamically source the recently proposed kinetic misalignment mechanism. The resulting universal enhancement of all axion interactions relative to those of the canonical QCD axion has a strong impact on the prospects of ALP experiments such as ALPS II , IAXO and many others. For instance, even Phase I of Casper Electric could discover this axion.