Resonant Signatures of Heavy Scalar Fields in the Cosmic Microwave Background

TL;DR

This paper explores how a heavy scalar field during inflation could produce distinctive resonant signatures in the CMB power spectrum, potentially explaining observed anomalies and offering insights into inflationary physics.

Contribution

It demonstrates that a heavy scalar field coupled derivatively can induce resonance effects in the primordial spectrum without disrupting slow-roll inflation, providing a novel mechanism for CMB anomalies.

Findings

Resonance can produce a sharp peak in the power spectrum.

The modulated spectrum can fit CMB data better than simple models.

Resonant signatures offer a way to detect heavy fields during inflation.

Abstract

We investigate the possibility that a heavy scalar field, whose mass exceeds the Hubble scale during inflation, could leave non-negligible signatures in the Cosmic Microwave Background (CMB) temperature anisotropy power spectrum through the parametric resonance between its background oscillations and the inflaton fluctuations. By assuming the heavy scalar field couples with the inflaton derivatively, we show that the resonance can be efficient without spoiling the slow-roll inflation. The primordial power spectrum modulated by the resonance has a sharp peak at a specific scale and could be an origin of the anomalies observed in the angular power spectrum of the CMB. In some values of parameters, the modulated spectrum can fit the observed data better than the simple power-law power spectrum, though the resultant improvement of the fit is not large enough and hence other observations such as non-Gaussianity are necessary to confirm that the CMB anomalies are originated from the resonant effect of the heavy scalar field. The resonant signatures can provide an opportunity to observe heavy degrees of freedom during inflation and improve our understanding of physics behind inflation.