BICEP2, non Bunch-Davies and Entanglement

TL;DR

This paper explores the implications of non Bunch-Davies vacuum states, viewed as entangled excited states, on the primordial gravitational wave spectrum and their potential to explain the BICEP2 results within inflationary models.

Contribution

It proposes interpreting non Bunch-Davies vacua as entangled excited states over the Bunch-Davies vacuum, linking entanglement to inflationary predictions.

Findings

Non Bunch-Davies vacua can be modeled as entangled squeezed states.

Such states may naturally account for the blue tilt in gravitational waves.

Entanglement properties are connected to the de Sitter horizon effects.

Abstract

BICEP2 result on the tensor to scalar ratio $r$ indicates a blue tilt in the primordial gravitational wave spectrum. This blue tilt and the observed large value $r = 0.2$ are difficult to accommodate within the single field inflationary scenarios under standard conditions. Non Bunch-Davies vacuum states have been proposed as a possibility. Such vacuua are known to lead to pathologies. In this note we propose to interpret them as excited/squeezed states built over the standard Bunch-Davies vacuum and discuss the associated entanglement properties due to de Sitter horizon, and how such an approach may be more natural in the context of inflation.