Dark energy is a cosmological constant
Cosmic acceleration is driven by a constant vacuum energy density (Λ), the simplest addition to general relativity consistent with the data.
1 open contradiction
- Evidential: These hypotheses draw opposite conclusions from the same evidence. Conflicts with There is no dark matter; gravity is modified (MOND).
Evidence balance
Supporting
2- Type Ia supernovae show accelerating expansionw70
Riess et al. · 1998 · Peer-reviewed
Supernova acceleration is the direct evidence for dark energy.
- Cosmic microwave background power spectrumw55
Planck Collaboration · 2020 · Peer-reviewed
ΛCDM fits the CMB with a cosmological constant.
Opposing
2- The cosmological constant problemw60
Steven Weinberg · 1989 · Peer-reviewed
The cosmological-constant problem is a deep theoretical strike against a naive Λ.
- The Hubble tensionw40
Riess et al. · 2022 · Peer-reviewed
The Hubble tension may indicate the simple Λ model is incomplete.
Assumptions
Dark energy density is constant in time
unjustified — Consistent with data but not proven.
General relativity is correct on cosmological scales
justified
Open questions within this hypothesis
- Why is Λ so small but nonzero?
- Does the Hubble tension signal new physics?
Falsification criteria
A measured time-variation in the dark-energy equation of state (w ≠ −1) would falsify the pure cosmological-constant model.