ϕ(2) or not ϕ(2): testing the simplest inflationary potential

Area of Science:

• Cosmology
• Inflationary theory
• Particle physics

Background:

• The simplest inflationary model, V=1/2m(2)ϕ(2), is the benchmark for future cosmological constraints.
• Deviations from this minimal scenario can be parametrized by a specific quantity that vanishes for a quadratic potential.

Purpose of the Study:

• To explore the implications of future constraints on inflationary models.
• To distinguish between a quadratic potential and a pseudo-Nambu-Goldstone boson model.
• To set limits on the deviation from unity of the speed of sound and the contribution of a second field to perturbations.

Main Methods:

• Analysis of a specific quantity related to the spectral index (n(s)) and tensor-to-scalar ratio (r).
• Calculation of bounds on physical parameters based on future observational uncertainties.
• Discussion of the impact of non-Gaussianity in light of recent BICEP2 results.

Main Results:

• The quantity (n(s)-1)+r/4+11(n(s)-1)(2)/24 vanishes for a quadratic potential (up to cubic slow-roll corrections).
• Future constraints can differentiate a quadratic potential from a pseudo-Nambu-Goldstone boson model (f≲30Mpl).
• Limits are set on |c(s)-1|≲3×10(-2) (Λ≳2×10(16) GeV) and second field contributions ≲6×10(-2).

Conclusions:

• The uncertainty in the spectral index is the limiting factor for these bounds.
• The error on the number of e-folds (ΔN≃0.4) implies an error on reheating temperature (ΔT(rh)/T(rh)≃1.2).
• The relevance of non-Gaussianity is discussed in the context of BICEP2 findings.