Bayesian Analysis of Inflation: Parameter Estimation for Single Field Models

TL;DR

This paper introduces ModeCode, a new computational tool for analyzing single field inflation models using current and future astrophysical data, enabling precise parameter estimation without slow roll approximation.

Contribution

ModeCode is a publicly available, numerically solving code for inflationary spectra, integrated with CAMB and CosmoMC, facilitating improved model constraints and future Bayesian comparisons.

Findings

Current data provide weak constraints on post-inflationary physics.

ModeCode's errors are negligible for Planck-level data.

Planck will significantly tighten inflationary model constraints.

Abstract

Future astrophysical datasets promise to strengthen constraints on models of inflation, and extracting these constraints requires methods and tools commensurate with the quality of the data. In this paper we describe ModeCode, a new, publicly available code that computes the primordial scalar and tensor power spectra for single field inflationary models. ModeCode solves the inflationary mode equations numerically, avoiding the slow roll approximation. It is interfaced with CAMB and CosmoMC to compute cosmic microwave background angular power spectra and perform likelihood analysis and parameter estimation. ModeCode is easily extendable to additional models of inflation, and future updates will include Bayesian model comparison. Errors from ModeCode contribute negligibly to the error budget for analyses of data from Planck or other next generation experiments. We constrain representative single field models (phi^n with n=2/3, 1, 2, and 4, natural inflation, and "hilltop" inflation) using current data, and provide forecasts for Planck. From current data, we obtain weak but nontrivial limits on the post-inflationary physics, which is a significant source of uncertainty in the predictions of inflationary models, while we find that Planck will dramatically improve these constraints. In particular, Planck will link the inflationary dynamics with the post-inflationary growth of the horizon, and thus begin to probe the "primordial dark ages" between TeV and GUT scale energies.