De Sitter vs Quintessence in String Theory

Recently, arguments for a refined de Sitter conjecture were put forward in [1]. Using the large distance conjecture of [2], the authors provide evidence for this dS conjecture in asymptotic regimes of field space, where the parametric control of string theory becomes arbitrarily good. Their main tool is Bousso's covariant entropy bound.[3] Here, we describe a simpler way to reach a similar conclusion. The argument is based on the fact that the cutoff of an effective theory with gravity decreases as the number of species grows. We then discuss a loophole in this argument and its possible counterpart in the assumptions underlying the entropy‐based derivation. The idea is to consider potentials which, while they remain below an exponentially falling bound, have small oscillations leading locally to relatively flat regions or even to an infinite series of dS minima.

Section: Introductionmentioning

confidence: 91%

The Asymptotic dS Swampland Conjecture ‐ a Simplified Derivation and a Potential Loophole

Hebecker

Wrase

2018

“…We would like to emphasize that this was the main idea presented in []. One may either criticize the ten‐dimensional approach from the start (as was done for instance in []) or accept it and argue about the proper implementation within 4 D supergravity.…”

Section: The Ten Dimensional Perspectivementioning

confidence: 99%

On uplifts by warped anti‐D3‐branes

Moritz

Retolaza

Westphal

2018

“…More natural models where the scalar couples to all particle species are typically ruled out by fifth‐force searches and solar system tests of gravity . It can also be difficult to realize the low energy scales required using stringy constructions …”

Section: Introductionmentioning

confidence: 99%

“…[155] It can also be difficult to realize the low energy scales required using stringy constructions. [67] In this paper we propose a stringy alternative to such considerations. The starting point is F-theory on a Spin (7) background; Spin (7) manifolds have recently been studied in a string theory context in [156][157][158][159].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Pixelated Dark Energy

Heckman

Lawrie

Lin

et al. 2019

We study the phenomenology of a recent string construction with a quantum mechanically stable dark energy. A mild supersymmetry protects the vacuum energy but also allows O(10−100) TeV scale superpartner masses. The construction is holographic in the sense that the 4D spacetime is generated from “spacetime pixels” originating from five‐branes wrapped over metastable five‐cycles of the compactification. The cosmological constant scales as Λ∼1/N in the pixel number. An instability in the construction leads to cosmic expansion. This also causes more five‐branes to wind up in the geometry, leading to a slowly decreasing cosmological constant which we interpret as an epoch of inflation followed by (pre‐)heating when a rare event occurs in which the number of pixels increases by an order one fraction. The sudden appearance of radiation triggers an exponential increase in the number of pixels. Dark energy has a time varying equation of state with wa=−3normalΩm,0false(1+w0false)/2, which is compatible with current bounds, and could be constrained further by future data releases. The pixelated nature of the Universe also implies a large‐l cutoff on the angular power spectrum of cosmological observables with l max ∼Ofalse(Nfalse). We also use this pixel description to study the thermodynamics of de Sitter space, finding rough agreement with effective field theory considerations.