Extended Models
Possible extensions of the simplest ΛCDM model are to allow quintessence rather than a cosmological constant. In this case, the equation of state of dark energy is allowed to differ from −1. Cosmic inflation predicts tensor fluctuations (gravitational waves). Their amplitude is parameterized by the tensor-to-scalar ratio (denoted r), which is determined by the energy scale of inflation. Other modifications allow for spatial curvature (Ωtot may be different from 1), hot dark matter in the form of neutrinos, or a running spectral index, which are generally viewed as inconsistent with cosmic inflation.
Allowing these parameters will generally increase the errors in the parameters quoted above, and may also shift the observed values somewhat.
| Parameter | Value | Description |
|---|---|---|
| Ωtot | Total density | |
| w | Equation of state of dark energy | |
| r | , k0 = 0.002Mpc−1 (2σ) | Tensor-to-scalar ratio |
| d ns / d ln k | , k0 = 0.002Mpc−1 | Running of the spectral index |
| Ωvh2 | Physical neutrino density | |
| Σmν | eV (2σ) | Sum of three neutrino masses |
Some researchers have suggested that there is a running spectral index, but no statistically significant study has revealed one. Theoretical expectations suggest that the tensor-to-scalar ratio r should be between 0 and 0.3, and the latest results are now within those limits.
Read more about this topic: Lambda-CDM Model
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