On primordial equation of state transitions

TL;DR

This paper analyzes the impact of primordial equation of state transitions on cosmic microwave background observations, concluding such transitions are unlikely to leave detectable imprints or explain certain anomalies.

Contribution

It demonstrates that pre-inflationary equation of state transitions are unlikely to produce observable effects in the CMB, constraining models of early universe physics.

Findings

Pre-inflationary transitions are unlikely to leave observable CMB imprints.

Transitions cannot easily explain the low multipole power suppression.

Observational bounds limit the amplitude of excitations from such transitions.

Abstract

We revisit the physics of transitions from a general equation of state parameter to the final stage of slow-roll inflation. We show that it is unlikely for the modes comprising the cosmic microwave background to contain imprints from a pre-inflationary equation of state transition and still be consistent with observations. We accomplish this by considering observational consistency bounds on the amplitude of excitations resulting from such a transition. As a result, the physics which initially led to inflation likely cannot be probed with observations of the cosmic microwave background. Furthermore, we show that it is unlikely that equation of state transitions may explain the observed low multipole power suppression anomaly.