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Gravitational waves in a codimension two braneworld

We consider the propagation of gravitational waves in six dimensions induced by sources living on 3-branes in the context of a recent exact solution (Mukohyama et al 2005 J. Cosmol. Astropart. Phys. JCAP07(2005)013). The brane geometries are de Sitter and the bulk is a warped geometry supported by a positive cosmological constant as well as a 2-form flux. We show that at low energies ordinary gravity is reproduced, and explicitly compute the leading corrections from six-dimensional effects. After regulating the brane we find a logarithmic dependence on the cut-off scale of brane physics even for modes whose frequency is much less than this energy scale. We discuss the possibility that this dependence can be renormalized into bulk or brane counterterms in line with effective field theory expectations. We discuss the inclusion of Gauss–Bonnet terms that have been used elsewhere to regulate codimension two branes. We find that such terms do not regulate codimension two branes for compact extra dimensions.