Global instability and dynamical compactification of internal spaces

String theory predicts extra dimensions in addition to the observed (3+1) dimensional space time.
Inspired by string theory, we propose a dynamical compactification mechanism for internal spaces. We
argue that the universe starts with higher-dimensional instability which causes the external universe to expand
and the internal space to shrink relatively. In the framework of Einstein, in order to realize this model, we
introduce the massive field and higher-order curvature terms. By introducing the Gauss-Bonnet term, we obtain
a stable cosmological solution, but it can not match our university. After continue to join the massive fields, we
obtain stable solutions whose external spatial dimension is only 1 or 2. Finally, we consider the third-order
Love lock gravity, and realize the idea of the origin of our universe.