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Résumé |
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 string loop 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 these vacua survive (presently unknown)
subleading corrections, and thus promote to full solutions of string theory. |
