Hartle-Hawking wave function and large-scale power suppression of CMB

TL;DR

This paper explores how the Hartle-Hawking wave function, via the Euclidean path integral approach, can account for large-scale power suppression in the CMB and discusses potential future applications like Euclidean wormholes.

Contribution

It demonstrates that the Hartle-Hawking wave function can explain large-scale CMB power suppression by selecting specific potential parameters, linking quantum cosmology to observable signatures.

Findings

Hartle-Hawking wave function can explain large-scale power suppression

Suitable potential parameters lead to observable effects

Potential future signatures include Euclidean wormholes

Abstract

In this presentation, we first describe the Hartle-Hawking wave function in the Euclidean path integral approach. After we introduce perturbations to the background instanton solution, following the formalism developed by Halliwell-Hawking and Laflamme, one can obtain the scale-invariant power spectrum for small-scales. We further emphasize that the Hartle-Hawking wave function can explain the large-scale power suppression by choosing suitable potential parameters, where this will be a possible window to confirm or falsify models of quantum cosmology. Finally, we further comment on possible future applications, e.g., Euclidean wormholes, which can result in distinct signatures to the power spectrum.