Abstract
The magnitude of primordial tensor perturbations reported by the BICEP2 experimentis consistent with simple models of chaotic inflation driven by a single scalarfield with a power-law potential ∝ ϕn : n ≃ 2, in contrastto the WMAP and Planck results, which favored modelsresembling the Starobinsky R+R2 model if running of the scalar spectral index could be neglected.While models of inflation with a quadratic potential may be constructed insimple N = 1 supergravity, these constructions are more challenging inno-scale supergravity. We discuss here how quadraticinflation can be accommodated within supergravity, focusing primarily on theno-scale case. We also argue thatthe quadratic inflaton may be identified with the supersymmetric partnerof a singlet (right-handed) neutrino, whose subsequent decay could havegenerated the baryon asymmetry via leptogenesis.
Highlights
General power-law potentialsWe work in the slow-roll approximation [6], where the magnitude of the scalar density perturbations implies that
Since no-scale supergravity arises as the effective field theory of compactified string theory [42], and is an attractive framework for sub-Planckian physics [43, 44], this is an appealing route towards embedding quadratic inflation in a more complete theory
We have shown that the BICEP2 data on r and the available data on ns are consistent (1.1) with a simple power-law, monomial, single-field model of inflation, and that V = m2φ2/2 is the power-law that best fits the available data (2.13)
Summary
We work in the slow-roll approximation [6], where the magnitude of the scalar density perturbations implies that. Since and η are both O(10−2), corresponding to V ∼ 0.1/MPl and V ∼ 0.01/MP2l, such a magnitude of the scalar spectral index would require ξ ∼ 0.01 and V ∼ 0.1/MP3l In this case, the variation in V over a range ∆φ = O(10MPl) is ∆V ∼ 1/MP2l, which is difficult to reconcile with the estimate of η from measurements of r and ns, and the slow-roll approximation in general. The 68% CL ranges indicated by BICEP2 and other experiments [1, 20, 21], r = 0.16+−00..0065, ns = 0.960±0.008, combined with the expected number of e-folds N = 50 ± 10, satisfy comfortably the consistency relation (2.11) This is not the case for the Planck upper limit on r if the scalar spectral index does not run, namely r < 0.08 at the 68% CL
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