How Well Can Future CMB Missions Constrain Cosmic Inflation?

TL;DR

Future CMB missions like PRISM and LiteBIRD are expected to significantly improve constraints on single-field slow-roll inflation models, potentially ruling out many scenarios and detecting subtle effects like slow-roll violations.

Contribution

This study evaluates the constraining power of upcoming CMB missions on inflationary models using Bayesian analysis and mock data simulations.

Findings

PRISM and LiteBIRD can rule out about 75% of inflationary scenarios.

PRISM can constrain scalar running and detect second-order slow-roll violations.

Future missions will challenge the potential-only description of inflation models.

Abstract

We study how the next generation of Cosmic Microwave Background (CMB) measurement missions (such as EPIC, LiteBIRD, PRISM and COrE) will be able to constrain the inflationary landscape in the hardest to disambiguate situation in which inflation is simply described by single-field slow-roll scenarios. Considering the proposed PRISM and LiteBIRD satellite designs, we simulate mock data corresponding to five different fiducial models having values of the tensor-to-scalar ratio ranging from $10^{-1}$ down to $10^{-7}$. We then compute the Bayesian evidences and complexities of all Encyclopaedia Inflationaris models in order to assess the constraining power of PRISM alone and LiteBIRD complemented with the Planck 2013 data. Within slow-roll inflation, both designs have comparable constraining power and can rule out about three quarters of the inflationary scenarios, compared to one third for Planck 2013 data alone. However, we also show that PRISM can constrain the scalar running and has the capability to detect a violation of slow roll at second order. Finally, our results suggest that describing an inflationary model by its potential shape only, without specifying a reheating temperature, will no longer be possible given the accuracy level reached by the future CMB missions.