Concept record · Atlas v1.2.0
Cosmological constant
Established resultWhat the term means here
A constant energy density of the vacuum, denoted Λ, entering Einstein equations as a uniform source. Positive Λ drives accelerated expansion; negative Λ gives anti-de Sitter geometry.
Why it matters to this question
The observed late-time acceleration of the universe is standardly modeled with a small positive Λ, and observations place the dark-energy equation of state near w = −1. That small positive number is the target any string construction has to reproduce, and it is the observational anchor of the whole debate.
What this does not establish
Modeling acceleration with a constant Λ is a successful description, not a demonstration that the vacuum energy is truly constant. Dynamical dark energy remains viable within current bounds, which is why the quintessence branch of this debate stays open.
Claims bearing on this concept · 4
- ds-001
The observed late-time acceleration of the universe is standardly modeled with a small positive cosmological constant, and current data place the dark-energy equation of state near w = −1.
- ds-008
An order-one value of c has been argued to be in tension with slow-roll inflation and with the observed value of the cosmological constant.
- ds-010
If metastable de Sitter vacua are excluded, dark energy would have to be dynamical — a rolling scalar field rather than a constant.
- ds-011
The Dark Dimension scenario ties the dark-energy scale to a Kaluza-Klein scale via the AdS distance conjecture, predicting a single extra dimension of roughly micron size.
Sources used for this record · 3
- Equation-of-state bounds on swampland quintessencearXiv:1808.02877
- News from the Swampland — constraining string theory with astrophysics and cosmologyarXiv:2307.15060
- Cosmological critique of the de Sitter conjecturearXiv:1808.09440