# Dark Energy in String Theory

Bento, Bruno Valeixo, Chakraborty, Dibya, Parameswaran, Susha L and Zavala, Ivonne
(2020) Dark Energy in String Theory. .

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## 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 K\"ahler potentials for bulk and local moduli, and leading superpotentials of the form $W = W_0 + A e^{-a \Phi}$ or $W = W_0 + A \Phi^p$. Conditions on the scalar potential imposed by supergravity are very restrictive, ruling out e.g. quintessence with $K=-n\ln(\Phi+\bar{\Phi})$ and $W = W_0+A \Phi^p$. Out of the examples considered, one can simultaneously satisfy $V>0$ and $\epsilon_V<1$ only for a deformation-like modulus with $K = k_0 + \frac{|\Phi|^{2n}}{k1}$ and a blow-up like modulus with $K=k_0 +\frac{(\Phi+\bar{\Phi})^{2n}}{k_1}$ when the leading order in the perturbative superpotential, $p$, is equal to $n$. We also review the scenario of Thermal Dark Energy, where thermal effects in a light hidden sector hold a scalar field up away from the minimum of its zero-temperature potential. This provides a viable model of Dark Energy with $w=-1$, consistent with known swampland conjectures, and motivates further early Thermal Dark Energy epochs with potentially observable consequences.

Item Type: Conference or Workshop Item (Unspecified) 23 pages, 4 figures, 3 tables, contribution to the proceedings of the Corfu Summer Institute 2019 "School and Workshops on Elementary Particle Physics and Gravity (CORFU2019)", includes work published in arXiv:1810.08634 (Olguin-Trejo, SLP, Tasinato, IZ) and arXiv:1907.10141 (Hardy, SLP), and some new results hep-th, hep-th, astro-ph.CO, gr-qc, hep-ph Faculty of Science and Engineering > School of Physical Sciences Symplectic Admin 08 Nov 2021 08:18 24 May 2022 07:11 https://arxiv.org/pdf/2005.10168 Author https://livrepository.liverpool.ac.uk/id/eprint/3142929