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v3.3.5
https://stockholmuniversity.zoom.us/j/530682073
As a consequence of the remarkable developments in cosmology over the past three decades, both in the theoretical as well as observational fronts, cosmic inflation has emerged as the leading scenario of the very early universe, setting natural initial conditions for the standard cosmological model prior to the commencement of the radiative hot Big Bang Phase. It is well known that the inflationary scenario often displays different sets of degeneracies in its predictions for the CMB observables. These degeneracies usually arise either because multiple inflationary models predict similar values for the scalar spectral index n_s and the tensor-to-scalar ratio r, or because within the same model, the values of {n_s, r} are insensitive to some of the model parameters, making it difficult for the CMB observations alone to constitute a unique probe of inflationary cosmology. Similarly another key aspect of inflationary cosmology, namely the epoch of 'reheating', also remains observationally inaccessible at present, despite a profusion of theoretical progress in this direction. After providing a consummate introduction of the inflationary cosmology, the speaker will demonstrate that by taking into account the constraints on the post-inflationary reheating parameters such as the duration of reheating, its temperature and especially its equation of state (EOS), it is possible to break this degeneracy in certain classes of inflationary models. The relic gravitational wave (GW) spectrum provides us with another tool to break inflationary degeneracies and probe the epoch of reheating. This is because the GW spectrum is sensitive to the post-inflationary EOS of the universe. Indeed a stiff EOS (w > 1/3) during reheating gives rise to a blue tilt in the spectral index of the GWs while a soft EOS (w<1/3) results in a red tilt.
Results discussed in this talk are based on the work
https://inspirehep.net/literature/1839228