We consider a 6-dimensional spacetime which is periodic in one of the extra
dimensions and compact in the other. The periodic direction is defined by
two 4-brane boundaries. Both static and nonstatic exact solutions, in which
the internal spacetime has a constant radius of curvature, are derived. In
the case of static solutions, the brane tensions must be tuned as in the 5
-dimensional Randall-Sundrum model; however, no additional fine-tuning is n
ecessary between the brane tensions and the bulk cosmological constant. By
further relaxing the sole fine-tuning of the model, we derive nonstatic sol
utions, describing de Sitter or anti-de Sitter 4-dimensional spacetimes. th
at allow for the fixing of the interbrane distance and the accommodation of
pairs of positive-negative and positive-positive tension branes. Finally,
we consider the stability of the radion field in these configurations by em
ploying small, time-dependent perturbations around the background solutions
. In analogy with results drawn in five dimensions. the solutions describin
g a de Sitter 4-dimensional spacetime turn out to be unstable while those d
escribing an anti-de Sitter geometry are shown to be stable.