Dark Energy in String Theory

Abstract

We consider various candidates for Dark Energy, motivated by string theory. Several no-go theorems push de Sitter string vacua, with w = −1, to the limits of theoretical control, and all known examples depend on a delicate interplay between different string theoretic ingredients. On the other hand, runaway moduli directions are ubiquitous in string theory, and could plausibly source slow-roll quintessence. We consider various candidate supergravity potentials, motivated by string theory, including single-field Kähler potentials for bulk and local moduli, and leading superpotentials of the form W = W 0 +Ae −aΦ or W = W 0 +AΦ p. Conditions on the scalar potential imposed by supergravity are very restrictive, ruling out e.g. quintessence with K = −n ln(Φ +Φ) and W = W 0 + AΦ p. Out of the examples considered, one can simultaneously satisfy V > 0 and * Includes work done in collaborations with Ed Hardy, Yessenia Olguin-Trejo, and Gianmassimo Tasinato. † Speaker.