Anomalies in the CMB from a cosmic bounce

Abstract

We explore a model of the early universe in which the inflationary epoch is preceded by a cosmic bounce, and argue that this scenario provides a common origin to several of the anomalous features that have been observed at large angular scales in the cosmic microwave background (CMB). More concretely, we show that a power suppression, a dipolar asymmetry, and a preference for odd-parity correlations, with amplitude and scale dependence in consonance with observations, are expected from this scenario. The model also alleviates the tension in the lensing amplitude. These signals originate from the indirect effect that non-Gaussian correlations between CMB modes and super-horizon wavelengths induce in the power spectrum. We follow a phenomenological approach, restricted to a family of bouncing models, and complement our analysis by pointing out to well established theories where our ideas are materialized. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.