De Sitter candidates in String Theory

by Dr Jakob Moritz (CERN)

Monday 8 Jul 2024, 13:00 → 14:00 Europe/Berlin

The simplest cosmology compatible with the accelerated expansion of our universe is de Sitter space. Yet, more than 25 years after the discovery of ``dark energy’’, concrete de Sitter vacua of string theory have remained elusive. In this talk I will present the first fully concrete string compactifications that yield, at leading order in the $g_s$ and $\alpha’$ expansions, de Sitter vacua of a form envisioned by Kachru, Kallosh, Linde and Trivedi (KKLT) more than 20 years ago. I will begin by reviewing the KKLT proposal and its complex set of delicately balanced ingredients. Then, I will show how all the required features come together in actual examples: I will define explicit Calabi-Yau orientifolds and choices of quantized fluxes, and derive the corresponding four-dimensional effective supergravity theories. Each example includes a strongly warped ``Klebanov-Strassler throat'' region containing a single anti-D3-brane, whose supersymmetry-breaking energy, computed at leading order in $\alpha'$, causes an uplift to a metastable de Sitter vacuum in which all moduli are stabilized. I will conclude by emphasizing a set of outstanding computational problems that need to be overcome in order to determine whether our vacua survive presently unknown subleading corrections, and thus promote to full solutions of string theory.