Impact of particle production during inflation on the CMB detection

TL;DR

This paper investigates how particle production during inflation affects gravitational waves and the CMB, finding that induced GWs are negligible for detection but influence the scalar spectral index, aligning with current observations.

Contribution

It introduces a nonminimally coupled particle production model during inflation and assesses its impact on gravitational waves and the scalar spectral index.

Findings

Induced GWs are only 0.3% of vacuum GWs at CMB scales.

Induced GWs have negligible impact on CMB B-mode polarization detection.

Particle production significantly affects the scalar spectral index n_s.

Abstract

This work focuses on particle production described by a nonminimally coupled model during inflation. In this model, three parameters determine the characteristic frequency and strength of the induced gravitational waves (GWs). Considering the impact of particle production on inflation, we identify the parameter values that generate the strongest GWs without violating the slow-roll mechanism at the CMB scale. However, even with such extreme parameters, the power spectrum of induced GWs is only about $0.3\%$ of that of vacuum GWs. This contribution remains insignificant when identifying the primary source of the detected CMB B-mode polarization. Furthermore, when our results are integrated with the constraints driven by P+ACT+LB+BK18, the contribution of induced GWs at CMB scales becomes negligible. In contrast, their impact on the scalar spectral index $n_s$ proves significant. For a range of parameter values, the Starobinsky inflation model yields predictions for $n_s$ that are consistent with the measurements obtained from P+ACT+LB+BK18.