| Abstract: |
In spite of its capability to explain the CP invariance of the QCD sector, QCD axion suffers from the quality issue as there can be contributions to the axion potential other than the QCD instanton. Particularly the global nature of the PQ symmetry poses challenges to the high quality of QCD axion. However, the understanding for the quality issue may be model-dependent: QCD axion can be understood as a dual description of a massive 2-form field. In that theory, differing from the understanding in the Peccei-Quinn picture, the axion quality concerns if there are other 3-forms coupled to the axion than the 3-form emergent in the low energy QCD. In this talk, we first discuss how the axion quality is defined and spoiled in the dual description. Based on this, we further discuss how to protect the quality of two form axion. Finally, we point out some phenomenological implications of the high quality axion in the dual description.
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