Predictions of just-enough inflation

TL;DR

This paper investigates a minimal inflation scenario with just enough expansion to match cosmological observations, analyzing perturbations and CMB anisotropies, and finds it consistent with current data unlike the simplest chaotic models.

Contribution

It introduces and tests a 'just-enough inflation' model with a quartic potential, showing it remains compatible with WMAP data and differs from standard slow-roll inflation.

Findings

The model fits WMAP 7-year data on large scales.

It does not explain the low power at the largest scales.

Violates slow-roll conditions at the largest scales.

Abstract

We find the best-fit cosmological parameters for a scenario of inflation with only the sufficient amount of accelerated expansion for the $\lambda\phi^4$ potential. While for the simplest scenario of chaotic inflation all observable primordial fluctuations cross the Hubble horizon during the slow-roll epoch, for the scenario of just-enough inflation the slow-roll conditions are violated at the largest length scales. Performing a numerical mode-by-mode integration for the perturbations on the largest scales and comparing the predicted anisotropies of the cosmic microwave background to results from the WMAP 7-yr data analysis, we find the initial conditions in agreement with current cosmological data. In contrast to the simplest chaotic model for the quartic potential, the just-enough inflation scenario is not ruled out. Although this scenario naturally gives rise to a modification of the first multipoles, for a quartic potential it cannot explain the lack of power at the largest angular scales.