Looking for Evidence of Scalar/Tensor Entanglement in the Cosmological Initial State

In standard approaches to inflationary cosmology it is taken as an assumption that the initial state of inflation is the Bunch-Davies vacuum. While it has been demonstrated that large deviations from Bunch-Davies fail to reproduce observations, it is possible that a more subtle deviation might reproduce the broad features we observe and provide additional detectable features. After giving a brief primer on the standard inflationary paradigm, I will introduce one such model that considers a small excitation of the Bunch-Davies vacuum where scalar and tensor modes are entangled, and the inflationary epoch lasts for the minimum time consistent with current observations. This model is of interest as it has the potential to reflect events like a bubble nucleation process occurring (relatively) shortly before the minimum ~60 e-foldings of inflation, as well as potentially explaining some unexplained features in the CMB power spectrum. I will then discuss the results of looking for features of this model within the Planck CMB data.