Localization of quantum fields on branes

A mechanism for localization of quantum fields on a s-brane, representing t he boundary of a (s + 2)-dimensional bulk space, is investigated. Minkowski and AdS bulk spaces are analyzed. Besides the background geometry, the rel evant parameters controlling the theory are the mass M and a real parameter eta, specifying the boundary condition on the brane. The importance of exp loring the whole range of allowed values for these parameters is emphasized . Stability in Minkowski space requires eta greater than or equal to -M, wh ereas in the AdS background all real eta are permitted. Both in the flat an d in AdS case, the induced field on the brane is a non-canonical generalize d free field. For a suitable choice of boundary condition, corresponding to the presence of a boundary state, the induced field on the brane mimics st andard (s + 1)-dimensional physics. In a certain range of eta, the spectral function in the the AdS case is dominated by a massive excitation, which i mitates the presence of massive particle on the brane. We show that the qua ntum field induced on the brane is stable. (C) 2001 Elsevier Science B.V. A ll rights reserved.