Conformally invariant braneworld and the cosmological constant

A six-dimensional braneworld scenario based on a model describing the interaction of gravity, gauge fields and 3 + 1 branes in a conformally invariant way is described. The action of the model is defined using a measure of integration built of degrees of freedom independent of the metric. There is no need to fine tune any bulk cosmological constant or the tension of the two (in the scenario described here) parallel branes to obtain zero cosmological constant, the only solutions are those with zero 4D cosmological constant. The two extra dimensions are compactified in a "football" fashion and the branes lie on the two opposite poles of the compact "football-shaped" sphere. (C) 2003 Elsevier B.V. All rights reserved.