Simple predictions from multifield inflationary models

Creating oscillons and oscillating kinks in two scalar field theories

Oscillons are time-dependent, localized in space, extremely long-lived states in nonlinear scalar-field models, while kinks are topological solitons in one spatial dimension. In the present work, we show new classes of oscillons and oscillating kinks in a system of two nonlinearly coupled scalar fields in 1+1 spatiotemporal dimensions. The solutions contain a control parameter, the variation of which produces oscillons and kinks with a flat-top shape. The model finds applications in condensed matter, cosmology, and high-energy physics.

Simple Emergent Power Spectra from Complex Inflationary Physics

We construct ensembles of random scalar potentials for N_{f}-interacting scalar fields using nonequilibrium random matrix theory, and use these to study the generation of observables during small-field inflation. For N_{f}=O(few), these heavily featured scalar potentials give rise to power spectra that are highly nonlinear, at odds with observations. For N_{f}≫1, the superhorizon evolution of the perturbations is generically substantial, yet the power spectra simplify considerably and become more predictive, with most realizations being well approximated by a linear power spectrum. This provides proof of principle that complex inflationary physics can give rise to simple emergent power spectra. We explain how these results can be understood in terms of large N_{f} universality of random matrix theory.

Gravitational wave consistency relations for multifield inflation

We study the tensor spectral index n(t) and the tensor-to-scalar ratio r in the simplest multifield extension to single-field, slow-roll inflation models. We show that multifield models with potentials V∼[under ∑]iλ_{i}|ϕ_{i}|^{p} have different predictions for n(t)/r than single-field models, even when all the couplings are equal λ_{i}=λ_{j}, due to the probabilistic nature of the fields' initial values. We analyze well-motivated prior probabilities for the λ_{i} and initial conditions to make detailed predictions for the marginalized probability distribution of n(t)/r. With O(100) fields and p>3/4, we find that n(t)/r differs from the single-field result of n(t)/r=-1/8 at the 5σ level. This gives a novel and testable prediction for the simplest multifield inflation models.