Stage IV CMB forecasts for warm inflation

TL;DR

Future CMB surveys like CMB-S4, Simons Observatory, and LiteBIRD are expected to significantly constrain warm inflation models, potentially detecting gravitational waves and distinguishing between different inflationary scenarios.

Contribution

This paper provides forecast constraints on warm inflation models using upcoming CMB data, highlighting the potential to detect gravitational waves and refine inflationary parameters.

Findings

All three surveys improve parameter constraints compared to current data.

Combined surveys can better distinguish warm inflation scenarios.

Some models may be excluded based on forecasted constraints.

Abstract

We report forecast constraints on warm inflation in the light of future cosmic microwave background (CMB) surveys, with data expected to be available in the coming decade. These observations could finally give us the missing information necessary to unveil the production of gravitational waves during inflation, reflected by the detection of a non-zero tensor-to-scalar ratio crucial to the B-mode power spectrum of the CMB. We consider the impact of three future surveys, namely the CMB-S4, Simons Observatory, and the space-borne $\textit{LiteBIRD}$, in restricting the parameter space of four typical warm inflationary models in the context of a quartic potential, which is well motivated theoretically. We find that all three surveys significantly improve the models' parameter space, compared to recent results obtained with current $\textit{Planck}$+BICEP/Keck Array data. Moreover, the combination of ground-based and space-borne (SO+$\textit{LiteBIRD}$ and CMB-S4+$\textit{LiteBIRD}$) surveys tightens the constraints so that we expect to distinguish even better warm inflation scenarios. This result becomes clear when we compare the models' predictions with a $\Lambda$CDM+$r$ forecast, compatible with $r=0$, in which one of them already becomes excluded by data.