Discordances in Cosmology and the Violation of Slow-Roll Inflationary Dynamics

Area of Science:

• Cosmology
• Theoretical Physics
• Astrophysics

Background:

• The standard Lambda cold dark matter (ΛCDM) model faces challenges with certain cosmological observations.
• Existing tensions exist between different datasets regarding key cosmological parameters like H₀ and S₈.

Purpose of the Study:

• To identify single-field inflationary models that improve the fit to Planck 2018 data.
• To alleviate tensions in cosmological parameter estimations, specifically H₀ and S₈.
• To explore inflationary trajectories beyond the slow-roll regime.

Main Methods:

• Investigated single-field inflationary models with features beyond the standard slow-roll approximation.
• Analyzed models with damped oscillations in the Hubble flow function or potential.
• Compared model fits to Planck 2018 data against a baseline ΛCDM model.

Main Results:

• Identified specific inflationary trajectories that improve Planck data fit.
• Demonstrated that these models can simultaneously increase H₀ and decrease S₈.
• Observed that localized oscillations in the primordial power spectrum mimic improvements seen with parameters like A<0xE2><0x82><0x97> or Ω<0xE2><0x82><0x96>.

Conclusions:

• Inflationary models with non-slow-roll features offer a compelling alternative to the standard model.
• These models show promise in resolving current cosmological tensions.
• Further tests using large-scale structure and CMB polarization data are crucial.