(Quasi)localized gauge field on a brane: dissipating cosmic radiation to extra dimensions?

We propose a mechanism ensuring (quasi)localization of massless gauge field s on a brane. The mechanism does not rely on BPS properties of the brane an d can be realized in any theory where charged particles are confined to the world-volume. The localized matter fluctuations induce a gauge kinetic ter m on the brane. At short distances the resulting propagator for the gauge f ield is identical to the four-dimensional propagator. The gauge theory on t he brane is effectively four-dimensional at short distances; it becomes hig her-dimensional on very large (cosmic) scales. The brane-bulk system exhibi ts the phenomenon of "infrared transparency". As a result, only very low fr equency modes can escape into extra dimensions. In this framework the large wavelength cosmic radiation can dissipate in extra space at a rate that ma y be observable, in principle. We briefly discuss some astrophysical conseq uences of this scenario. The same mechanism of localization of gauge fields may work in Kaplan's fra mework for domain wall chiral fermions on lattices. (C) 2001 Published by E lsevier Science B.V.