Emergent de Sitter Cosmology from Decaying Anti–de Sitter Space

Recent developments in string compactifications demonstrate obstructions to the simplest constructions of low energy cosmologies with positive vacuum energy. The existence of obstacles to creating scale-separated de Sitter solutions indicates a UV/IR puzzle for embedding cosmological vacua in a unitary theory of quantum gravity. Motivated by this puzzle, we propose an embedding of positive energy Friedmann-Lemaître-Robertson-Walker cosmology within string theory. Our proposal involves confining 4D gravity on a brane which mediates the decay from a nonsupersymmetric five-dimensional anti–de Sitter false vacuum to a true vacuum. In this way, it is natural for a 4D observer to experience an effective positive cosmological constant coupled to matter and radiation, avoiding the need for scale separation or a fundamental de Sitter vacuum.

Figure 1

The 4D CC as a function of tension.

Figure 2

Potential (in Poincaré coordinates) experienced by graviton modes (solid line) and the corresponding zero mode in domain wall coordinates (dotted line).

Figure 3

An artist’s impression of a $(p,q)5$ braneworld.