The final release of the 2018 PLANCK results using full mission data have been published.
The 6-parameter ΛCDM model continues to provide an excellent fit to the cosmic microwave background data at high and low redshift, describing the cosmological information in over a billion map pixels with just six parameters. With 18 peaks in the temperature and polarization angular power spectra constrained well, Planck measures five of the six parameters to better than 1 (simultaneously), with the best-determined parameter (θ∗) now known to 0.03 .
The age is the universe is 13.787 ± 0.020 billion years old.
Planck temperature, polarization, and lensing data determine the spectral index of scalar perturbations to be ns=0.9649±0.0042 at 68% CL and show no evidence for a scale dependence of ns. Spatial flatness is confirmed at a precision of 0.4% at 95% CL with the combination with BAO data. The Planck 95% CL upper limit on the tensor-to-scalar ratio, r0.002<0.10, is further tightened by combining with the BICEP2/Keck Array BK14 data to obtain r0.002<0.064. In the framework of single-field inflationary models with Einstein gravity, these results imply that: (a) slow-roll models with a concave potential, V"(ϕ)<0, are increasingly favoured by the data; and (b) two different methods for reconstructing the inflaton potential find no evidence for dynamics beyond slow roll. Non-parametric reconstructions of the primordial power spectrum consistently confirm a pure power law.
Inflation is confirmed.
Assumptions underlying ΛCDM and confirmed by Planck
A1 Physics is the same throughout the observable Universe.
A2 General Relativity (GR) is an adequate description of gravity.
A3 On large scales the Universe is statistically the same everywhere
(initially an assumption, or “principle,” but now
strongly implied by the near isotropy of the CMB).
A4 The Universe was once much hotter and denser and has been
expanding since early times.
A5 There are five basic cosmological constituents:
(a) Dark energy that behaves just like the energy density of
(b) Dark matter that is pressureless (for the purposes of
forming structure), stable and interacts with normal matter
(c ) Regular atomic matter that behaves just like it does on
(d) The photons we observe as the CMB.
(e) Neutrinos that are almost massless (again for structure
formation) and stream like non-interacting, relativistic
particles at the time of recombination.
A6 The curvature of space is very small.
A7 Variations in density were laid down everywhere at early
times, and are Gaussian, adiabatic, and nearly scale invariant
(i.e., proportionally in all constituents and with similar
amplitudes as a function of scale) as predicted by inflation.
A8 The observable Universe has “trivial” topology (i.e., like R
3 In particular it is not periodic or multiply connected.