Cosmological solution in M-theory on S1/Z2

We provide the first example of a cosmological solution of the Horava-Witten supergravity. This solution is obtained by exchanging the role of time with the radial coordinate of the transverse space to the five-brane soliton. On the boundary, this corresponds to rotating an instanton solution into a tunneling process in a space with Lorentzian signature, leading to an expanding universe. Due to the freedom to choose different nontrivial Yang-Mills backgrounds on the boundaries, the two walls of the universe (visible and hidden worlds) expand differently. However at late times the anisotropy is washed away by gravitational interactions.