Vacuum Sampling in the Landscape during Inflation

TL;DR

This paper explores how sampling multiple vacua during inflation leads to domain walls and black holes, with constraints on their energy scales to ensure consistency with Big Bang Nucleosynthesis.

Contribution

It analyzes the phenomenological implications of vacuum sampling during inflation, deriving bounds on the barrier scale to prevent cosmological conflicts.

Findings

Success of BBN requires barrier scale μ > 10 TeV for non-degenerate vacua.

If vacua are nearly degenerate, black holes form with μ > 10^{-5} M_P.

Black holes from domain walls must evaporate to avoid dark matter overproduction.

Abstract

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 $\mu$ of the barriers that partition the accessed vacua. We find that the success of Big Bang Nucleosynthesis (BBN) implies $\mu \gsim 10$ TeV, as long as the sampled vacua have a non-degeneracy larger than $\cal{O}({{\rm MeV}}^{\rm 4})$. 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 $\mu \gsim 10^{-5}M_P$. These black holes are not allowed to survive and contribute to cosmic dark matter density.