title: Widening the Axion Window via Kinetic and Stückelberg Mixings.
abstract: We point out that kinetic and Stückelberg mixings that are generically present in the low energy effective action of axions can significantly widen the window of axion decay constants. We show that an effective super-Planckian decay constant can be obtained even when the axion kinetic matrix has only sub-Planckian entries. Our minimal model involves only two axions, a Stückelberg U(1) and a modest rank instanton generating non-Abelian group. Below the mass of the Stückelberg U(1), there is only a single axion with a nonperturbatively generated potential. In contrast to previous approaches, the enhancement of the axion decay constant is not tied to the number of degrees of freedom introduced. We also discuss how kinetic mixings can lower the decay constant to the desired axion dark matter window. String theory embeddings of this scenario and their phenomenological features are briefly discussed.
authors.affiliation: Department of Physics, 1150 University Avenue, University of Wisconsin, Madison, Wisconsin 53706, USA.|Center for Fundamental Physics and Institute for Advanced Study, Hong Kong University of Science and Technology, Hong Kong.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Gary
authors.initials: G
authors.lastname: Shiu
authors.affiliation: Instituto de Física Teórica UAM-CSIC, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Wieland
authors.initials: W
authors.lastname: Staessens
authors.affiliation: Department of Physics, 1150 University Avenue, University of Wisconsin, Madison, Wisconsin 53706, USA.|Center for Fundamental Physics and Institute for Advanced Study, Hong Kong University of Science and Technology, Hong Kong.
authors.forename: Fang
authors.initials: F
authors.lastname: Ye