Gravitational Instabilities of Spacetime

Theories with compact extra dimensions can be unstable to decay into a bubble of nothing -- an instability that results in the destruction of spacetime. In this talk, I will discuss whether bubbles of nothing can exist in realistic theories where the moduli field responsible for setting the size of the extra dimensions is stabilized at a positive value of the vacuum energy. Using bottom-up methods, and focusing on a five-dimensional toy model, I will argue that four-dimensional de Sitter vacua admit bubbles of nothing for a wide class of stabilizing potentials. I will show that, unlike ordinary Coleman-De Luccia tunneling, the corresponding decay rate remains non-zero in the limit of vanishing vacuum energy, and that it can be faster than decay channels previously discussed in the literature. I will discuss potential implications on the physics of vacuum selection, as well as on the possibility of creating a Universe from "nothing".