PHYS08200605006 D.K. Hazra - Homi Bhabha National Institute

Chapter 8
Summary and outlook
In this final chapter, after a rapid summary of the main conclusions of this thesis, we shall
outline a few of the issues that arise as a logical consequence of the problems investigated
here and require to be followed up.
8.1 Summary
In this thesis work, we were primarily interested on two aspects, viz. features in the primordial
spectrum and non-Gaussianities.
In the context of primordial features, we had focussed on investigating the extent to
which the recent CMB data permitted the presence of local as well as non-local features
in the inflationary perturbation spectrum. We had found that localized features such a
burst of oscillations generated due to a step in inflationary potentials leads to a better fit
to the data than the more conventional featureless and nearly scale invariant primordial
spectrum [85]. Interestingly, we had also found that certain repeated patterns, such as
persistent modulations, which are produced due to a resonant phenomenon occurring in
potentials with oscillatory terms, also result in an improved fit to the data [101]. Preliminary
analysis suggest that ongoing missions such as Planck [20] will be able to help us
arrive at stronger constraints on such features [87, 101].
It has been increasingly recognized that the detection of non-Gaussianities, in particular,
a non-zero bi-spectrum (i.e. the three point correlator of the curvature perturbation)
can act as a powerful discriminator amongst the plethora of inflationary models that are
consistent with the data at the level of the power spectrum. With the aim of studying
non-Gaussianities generated in inflationary models that lead to features in the power
spectrum, using the Maldacena formalism, we had developed a numerical code to effi-
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