Constraining Primordial Black Hole Formation from Single-Field Inflation

Area of Science:

• Cosmology
• Theoretical Physics
• Astrophysics

Background:

• Primordial black holes (PBHs) are hypothetical compact stellar objects formed in the early universe.
• Their formation is often linked to the collapse of large-amplitude perturbations during single-field inflation.
• Understanding PBH formation mechanisms is key to probing early universe physics.

Purpose of the Study:

• To investigate the one-loop correction to the large-scale power spectrum in inflationary models with a sharp transition in the second slow-roll parameter.
• To determine if models that produce significant amounts of PBHs have observable imprints on large-scale structures.

Main Methods:

• Calculation of one-loop corrections to the power spectrum.
• Analysis of inflationary models featuring a sharp transition in the second slow-roll parameter.
• Comparison of theoretical predictions with observational constraints from the cosmic microwave background (CMB).

Main Results:

• Models generating a substantial abundance of primordial black holes induce nonperturbative coupling on large scales.
• This large-scale coupling is detectable by cosmic microwave background radiation observations.
• A significant link exists between small-scale perturbations and large-scale cosmological observations.

Conclusions:

• Large-scale cosmological observations, particularly those probing the cosmic microwave background, can constrain models of primordial black hole formation.
• The study implies that the power spectrum on small scales, relevant for PBH production, is indirectly constrained by large-scale measurements.
• This work highlights the interconnectedness of small-scale and large-scale physics in the early universe.