Axion model in extra dimensions with TeV scale gravity

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Abstract
A simple axion model is proposed in the scenario of large extra dimensions where the gravity scale is as low as 1 TeV. To obtain an intermediate-scale decay constant of the axion, the axion is assumed to live in a subspacetime (brane) of the whole bulk. In this model there appear Kaluza-Klein modes of the axion which have a stronger interaction than those of the graviton. The axion brane plays the role of an absorber of the graviton Kaluza-Klein modes. For these reasons, the phenomenology and cosmology of the axion become highly nontrivial. We discuss various cosmological constraints as well as astrophysical ones and show that the model is viable for certain choices of the dimensionality of the axion brane. The structure of the model proposed here provides a viable realization of the fat brane idea to relax the otherwise very severe cosmological constraints.