Stringy signals from large-angle correlations in the cosmic microwave background?

TL;DR

This paper suggests that anomalies in large-angle correlations and parity imbalance in the CMB could be signals of string-inspired physics, linked to a composite inflaton field and boundary conditions affecting the power spectrum.

Contribution

It introduces a novel interpretation of CMB anomalies as stringy signals arising from boundary conditions of a composite inflaton, without relying on specific models.

Findings

Infrared cutoffs linked to boundary conditions explain observed anomalies.

Parity imbalance may originate from fermionic boundary conditions.

No specific inflation model is required for this interpretation.

Abstract

We interpret the lack of large-angle temperature correlations and the apparent even-odd parity imbalance, observed in the cosmic microwave background by COBE, WMAP and Planck satellite missions, as a possible stringy signal ultimately stemming from a composite inflaton field (e.g. a fermionic condensate). Based on causality arguments and a Fourier analysis of the angular two-point correlation function, two infrared cutoffs $k_{\rm min}^{\rm even,odd}$ are introduced in the CMB power spectrum associated, respectively, with periodic and antiperiodic boundary conditions of the fermionic constituents (echoing the Neveu-Schwarz-Ramond model in superstring theory), without resorting to any particular model.