The cosmological constant in the brane world of string theory on $S^{1}/Z_{2}$

Understand

Orbifold branes in string theory are investigated, and the general field equations on the branes are given explicitly for type II and heterotic string.

• It is shown that the effective cosmological constant on each of the two branes can be easily lowered to its current observational value, using large extra dimensions.
• This is also true for type I string.
• The radion stability is studied by using the Goldberger-Wise mechanism, and shown explicitly that it is stable.