Vacuum sampling in the landscape during inflation

We consider the phenomenological consequences of sampling multiple vacua during inflation motivated by an enormous landscape. A generic consequence of this sampling is the formation of domain walls, characterized by the scale μ of the barriers that partition the accessed vacua. We find that the success of big bang nucleosynthesis (BBN) implies μ 10TeV, as long as the sampled vacua have a nondegeneracy larger than O(MeV4). Otherwise, the walls will dominate and eventually form black holes that must reheat the universe sufficiently for BBN to take place; in this case, we obtain μ 10-5MP. These black holes are not allowed to survive and contribute to cosmic dark matter density.