Classiication of 5-dimensional Space-time with Parallel 3-branes

If the fth dimension is one-dimensional connected manifold, up to diieo-morphic, the only possible space-time will be M =Z 2. And there exist two possibilities on cosmology constant: the cosmology constant is constant along the fth dimension, and the cosmology constant is sectional constant along the fth dimension. We construct the general models with parallel 3-branes on those kinds of the space-time and with constant/sectional constant cosmology constant, and point out that for compact fth dimension, the sum of the brane tensions is zero, for non-compact fth dimension, the sum of the brane tensions is positive. We assume the observable brane which includes our world should have positive tension, and obtain that in those general scenarios, the 5-dimensional GUT scale on each brane can be indentiied as the 5-dimensional Planck scale, but, the 4-dimensional Planck scale is generated from the low 4-dimensional GUT scale exponentially in our world. We also give some simple models to show explicitly how to solve the gauge hierarchy problem.