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

We propose a mechanism ensuring (quasi)localization of massless gauge fields on a brane. The mechanism does not rely on BPS properties of the brane and can be realized in any theory where charged particles are confined to the world-volume. The localized matter fluctuations induce a gauge kinetic term on the brane. At short distances the resulting propagator for the gauge field is identical to the four-dimensional propagator. The gauge theory on the brane is effectively four-dimensional at short distances; it becomes higher-dimensional on very large (cosmic) scales. The brane-bulk system exhibits the phenomenon of "infrared transparency". As a result, only very low frequency modes can escape into extra dimensions. In this framework the large wavelength cosmic radiation can dissipate in extra space at a rate that may be observable, in principle. We briefly discuss some astrophysical consequences of this scenario. The same mechanism of localization of gauge fields may work in Kaplan's framework for domain wall chiral fermions on lattices. (C) 2001 Published by Elsevier Science B.V.