Cosmic Inflation at the Crossroads
arxiv(2024)
摘要
The capability of Cosmic Inflation to explain the latest Cosmic Microwave
Background and Baryonic Acoustic Oscillation data is assessed by performing
Bayesian model comparison within the landscape of nearly three-hundred models
of single-field slow-roll inflation. We present the first Bayesian data
analysis based on the third-order slow-roll primordial power spectra. In
particular, the fourth Hubble-flow function ϵ_4 remains unbounded
while the third function verifies, at two-sigma, ϵ_3∈[-0.4,0.5],
which is perfectly compatible with the slow-roll predictions for the running of
the spectral index. We also observe some residual excess of B-modes within
the BICEP/Keck data favoring, at a non-statistically significant level,
non-vanishing primordial tensor modes: log(ϵ_1) > -3.9, at 68%
confidence level. Then, for 283 models of single-field inflation, we compute
the Bayesian evidence, the Bayesian dimensionality and the marginalized
posteriors of all the models' parameters, including the ones associated with
the reheating era. The average information gain on the reheating parameter
R_reh reaches 1.3 ± 0.18 bits, which is more than a factor two
improvement compared to the first Planck data release. As such, inflationary
model predictions cannot meet data accuracy without specifying, or
marginalizing over, the reheating kinematics. We also find that more than
40% of the scenarios are now strongly disfavored, which shows that the
constraining power of cosmological data is winning against the increase of the
number of proposed models. In addition, about 20% of all models have
evidences within the most probable region and are all favored according to the
Jeffreys' scale of Bayesian evidences.
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