Inflationary perturbations, quantum theory and modified gravity

The success of the inflationary paradigm rests on its ability to explain the observed classicality of primordial quantum fluctuations despite their quantum origin.  Squeezing of primordial cosmological inhomogeneities along with the mechanism of decoherence accounts for many aspects of this quantum to classical transition, although it remains a matter of debate as to whether this is sufficient to explain the issue of realization of a single outcome from a quantum ensemble given that the universe is a closed system. Apart from decoherence there have been attempts to resolve this issue through Continuous Spontaneous Localization (CSL), which is a stochastic nonlinear modification of the non-relativistic Schrodinger equation. In this talk, I shall revisit one such recently proposed working model of classicalization by spontaneous collapse to look for possible modifications to scalar and tensor power spectra and their implications. I shall show that it can potentially change the consistency relation of single-field models and a precise measurement of tensor spectral tilt and its running could serve as a test of such dynamics in the early universe.
In the later part of my talk, I shall be discussing the cosmological features of a modified theory of gravity known as Fourth Order Gravity (FOG), having a free length parameter, and no cosmological constant or dark energy. By making a suitable choice for the present Hubble parameter and value of third derivative of the scale factor (the jerk), I shall show  that the model can explain several cosmological features (like the late time cosmic acceleration) of the present universe to the same degree of accuracy as the standard concordance model, irrespective of whether the length parameter is constant or time-dependent.