Horizon ratio bound for inflationary fluctuations

Area of Science:

• Cosmology
• Theoretical Physics
• Astrophysics

Background:

• Cosmic inflation is a theoretical period of rapid expansion in the early universe.
• Gravity waves are primordial ripples in spacetime predicted to originate from inflation.
• The cosmic microwave background (CMB) provides crucial data for testing inflationary models.

Purpose of the Study:

• To establish a robust upper bound on the wavelength-to-horizon ratio at the end of inflation.
• To constrain the number of e-folds (N) for gravity wave modes.
• To assess the viability of specific inflationary models, such as chaotic inflation with a phi^4 potential.

Main Methods:

• Analysis of the gravity wave background amplitude.
• Derivation of theoretical upper bounds based on cosmic energy density evolution.
• Comparison of derived bounds with observational data from CMB anisotropies.

Main Results:

• A robust upper bound is found for the wavelength-to-horizon ratio: lambda/H(-1) <= e(60).
• This implies that the number of e-folds (N) is approximately less than or equal to 67 for vast classes of slow-roll models.
• The derived bound closes the 'escape hatch' for large N values (>62) in chaotic inflation models with a phi^4 potential.

Conclusions:

• The study solidifies the tension between CMB observations and certain inflationary models.
• The findings provide a powerful constraint on the duration and characteristics of cosmic inflation.
• Future observational data will be crucial for further refining these cosmological constraints.