Gravitational wave consistency relations for multifield inflation

Area of Science:

• Cosmology
• Theoretical Physics
• Particle Physics

Background:

• Cosmic inflation is a leading theory explaining the early universe's rapid expansion.
• Single-field, slow-roll inflation models provide a baseline for cosmological predictions.
• Multifield extensions offer richer phenomenology but require careful theoretical analysis.

Purpose of the Study:

• To investigate the predictions of the simplest multifield inflation models for key cosmological observables.
• To compare the predictions of multifield models with those of single-field models.
• To identify testable signatures distinguishing multifield inflation.

Main Methods:

• Analysis of the tensor spectral index (n(t)) and tensor-to-scalar ratio (r) in multifield models.
• Consideration of potentials of the form V∼∑ᵢλᵢ|ϕᵢ|ᵖ.
• Investigation of the impact of probabilistic initial field values and couplings.
• Calculation of marginalized probability distributions for n(t)/r.

Main Results:

• Multifield models yield different predictions for n(t)/r compared to single-field models, even with equal couplings.
• The probabilistic nature of initial field values is crucial for these distinctions.
• With approximately 100 fields and p>3/4, n(t)/r deviates from the single-field prediction (n(t)/r=-1/8) at the 5σ level.

Conclusions:

• The simplest multifield inflation models provide novel and testable predictions.
• Observational constraints on n(t) and r could potentially distinguish between single-field and multifield inflationary scenarios.
• This work highlights the importance of considering multifield dynamics in early universe cosmology.