Orbifold branes in string/M-Theory and their cosmological applications
  In this brief report, we summarize our recent studies in brane cosmology in
both string theory and M-Theory on $S^{1}/Z_{2}$. In such setups, we find that
the radion is stable and its mass, with a very conservative estimation, can be
of the order of $0. 1 \sim 0.01$ GeV. The hierarchy problem can be addressed by
combining the large extra dimension, warped factor, and tension coupling
mechanisms. Gravity is localized on the visible brane, and the spectrum of the
gravitational Kaluza-Klein (KK) modes is discrete and can have a mass gap of
TeV. The corrections to the 4D Newtonian potential from the higher order
gravitational KK modes are exponentially suppressed. Applying such setups to
cosmology, we find that a late transient acceleration of the universe seems to
be the generic feature of the theory, due to the interaction between branes and
bulk. A bouncing early universe is also rather easily realized.
