The simplest single-field inflation models capture all the relevant contributions to the patterns in the Cosmic Microwave Background (CMB) observed today. A key assumption in these models is that the quantum inflationary fluctuations that source such patterns are generated by a particular quantum state — the Bunch-Davies (BD) state. While this is a well-motivated choice from a theoretical perspective, the question arises of whether current data can rule out other, also well motivated, choices of states. In particular, as we previously demonstrated in [1], entanglement is naturally and inevitably dynamically generated during inflation given the presence of a “rolling” spectator scalar field — and the resulting entangled state will yield a primordial power spectrum with potentially measurable deviations compared to the canonical BD result. For this work we developed a perturbative framework to allow a systematic exploration of constraints on (or detection of) entangled states with Planck CMB data using Monte Carlo techniques. We have found that most entangled states accessible with our framework are consistent with the data. One would have to expand the framework to allow a greater variety of entangled states in order to saturate the Planck constraints and more systematically explore any preferences the data may have among the different possibilities.
Several cosmological tensions have emerged in light of recent data, most notably in the inferences of the parameters H0 and σ8. We explore the possibility of alleviating both these tensions simultaneously by means of the Albrecht-Skordis "quintessence" potential. The field can reduce the size of the sound horizon r * s while concurrently suppressing the power in matter density fluctuations before it comes to dominate the energy density budget today. Interestingly, this rich set of dynamics is governed entirely by one free parameter that is of O(10) in Planck units. We find that the inferred value of H0 can be increased, while that of σ8 can be decreased, both by ≈ 1σ compared to the ΛCDM case. However, ultimately the model is disfavored by Planck and BAO data alone, compared to the standard ΛCDM model, with a ∆χ 2 ≈ +6. When including large scale structure and supernova data ∆χ 2 ≈ +1. We note that historically much attention has been focused on preserving the three angular scales θD, θEQ, and θ * s to their ΛCDM values. Our work presents an example of how, while doing so indeed maintains a relatively good fit to the CMB data for an increased number of ultra-relativistic species, it is a-priori insufficient in maintaining such a fit in more general model spaces.
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