Simple predictions from multifield inflationary models

Area of Science:

• Cosmology
• Theoretical Physics
• Inflationary Cosmology

Background:

• Inflationary cosmology is a key paradigm for explaining the early universe.
• Multifield models offer a richer framework than single-field models.
• Unambiguous predictions for observable quantities are crucial for testing these models.

Purpose of the Study:

• To investigate the predictive power of multifield inflationary models.
• To determine if N-quadratic inflation makes unambiguous predictions for cosmological observables.
• To explore the impact of the number of fields (N) on these predictions.

Main Methods:

• Numerical evaluation of perturbation equations for N=2, 3, and O(100) fields.
• Utilizing distinct methods for specifying initial conditions of background fields.
• Employing Monte Carlo sampling to analyze probability distributions of observables.

Main Results:

• All multifield scenarios studied are highly predictive.
• Probability distributions for cosmological observables become sharply peaked as N increases.
• For N=100 fields, specific ranges for spectral index (ns), running (α), tensor-to-scalar ratio (r), and isocurvature-to-adiabatic ratio (riso) were obtained with high confidence (95%).

Conclusions:

• Multifield inflationary models, particularly N-quadratic inflation, provide unambiguous predictions.
• The number of fields significantly enhances the predictive power of these models.
• Growing isocurvature perturbation amplitudes with N suggest sensitivity to post-inflationary physics, opening new testing avenues.