Inflation models and observation

Abstract

We consider small-field models which invoke the usual framework for the effective field theory, and large-field models which go beyond that. Present and future possibilities for discriminating between the models are assessed, on the assumption that the primordial curvature perturbation is generated during inflation. With PLANCK data, the theoretical and observational uncertainties on the spectral index will be comparable, providing useful discrimination between small-field models.Further discrimination between models may come later through the tensor fraction, the running of the spectral index and non-gaussianity. The prediction for the trispectrum in a generic multi-field inflation model is given for the first time.

Non-Gaussianity from the inflationary trispectrum

“…They find that |f NL | is typically small in the socalled "horizon-crossing approximation", where the fields roll to their minima after inflation with values that are negligible compared to those at horizon crossing. The same conclusion was reached by Alabidi & Lyth [27], and by Kim & Liddle [43], who used the horizon-crossing approximation to compute the non-linearity parameters for multi-field models with monomial potentials. Recently, Battefeld & Easther [57] have extended the analysis of Vernizzi & Wands to an arbitrary number of scalar fields and have found the corresponding form of the non-linearity parameter f NL without assuming the horizon-crossing approximation.…”

“…It has recently become clear that a great deal of important information is encoded in the non-linearities of the curvature perturbation [15,16,17,18,19]. The lower-order moments of ζ are conventionally expressed in terms of the non-linearity parameters f NL [20,21,22] and τ NL [23,24,25,26,27], which respectively quantify the importance of the three-and four-point correlators of ζ relative to the power spectrum. To date, primordial non-gaussian features in the CMB have yet to be detected and the current upper bounds on the non-linearity parameters are |f NL | 10 2 [1,28,29] and |τ NL | 10 8 [27].…”

“…The lower-order moments of ζ are conventionally expressed in terms of the non-linearity parameters f NL [20,21,22] and τ NL [23,24,25,26,27], which respectively quantify the importance of the three-and four-point correlators of ζ relative to the power spectrum. To date, primordial non-gaussian features in the CMB have yet to be detected and the current upper bounds on the non-linearity parameters are |f NL | 10 2 [1,28,29] and |τ NL | 10 8 [27]. A major goal for the next generation of CMB experiments will be to improve on these bounds, and the Planck satellite is expected to be sensitive to |f NL | ∼ 5 [21] and |τ NL | ∼ 560 [24].…”

Inflation and String Theory

“…We will assume that φ end M pl . If the higher-order terms in (2.58) are irrelevant when the pivot scale exits the horizon, then the spectral tilt and the tensor-to-scalar ratio are [215,216] n s − 1 = 2η 0 , (2.59)…”

Predictions of dynamically emerging brane inflation models

“…[67] The limit p → −∞ of [41] corresponds to an exponential potential like the one discussed in this article; however, no estimate of r and nT , which depend on the exponent α, were given, and the WMAP3 data set alone was used for comparison. This led Alabidi and Lyth to conclude that an exponential potential would be allowed at the 2σ level.…”