Is a step in the primordial spectral index favoured by CMB data?

Joy, Minu ; Shafieloo, Arman ; Sahni, Varun ; Starobinsky, Alexei A. (2009) Is a step in the primordial spectral index favoured by CMB data? Journal of Cosmology and Astroparticle Physics, 2009 . 028_1-028_8. ISSN 1475-7516

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Official URL: http://iopscience.iop.org/1475-7516/2009/06/028

Related URL: http://dx.doi.org/10.1088/1475-7516/2009/06/028

Abstract

A sudden small change in the second derivative of the inflaton potential can result in a universal local feature in the spectrum of primordial perturbations generated during inflation. The exact solution describing this feature is characterized by a step in the spectral index modulated by characteristic oscillations and results in a large running of the spectral index localized over a few e-folds of scale. In this paper we confront this step-like feature with the 5 year WMAP results and demonstrate that it provides a better fit to this data than a featureless initial spectrum. If such a feature exists at all, then it should lie at sufficiently large scales k0 ≳ 0.003 Mpc−1 corresponding to l ≳ 40. The sign of the effect is shown to correspond to the negative running of ns localized near this scale. This feature could arise as a result of a 'mini-waterfall'-type fast second order phase transition experienced by an auxiliary heavy field during inflation, in a model similar to hybrid inflation (though for a different choice of parameters). If this is the case, then the auxiliary field should be positively coupled to the inflaton.

Item Type:Article
Source:Copyright of this article belongs to Institute of Physics.
Keywords:Inflation; Physics of the Early Universe
ID Code:47354
Deposited On:11 Jul 2011 05:42
Last Modified:11 Jul 2011 05:42

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