Inflationary paradigm after Planck 2013

TL;DR

This paper reviews the inflationary paradigm in cosmology, emphasizing its compatibility with Planck 2013 data and defending its theoretical robustness against recent criticisms, reaffirming its status as a leading model of the early universe.

Contribution

It provides a comprehensive analysis of inflation models post-Planck 2013, addressing criticisms and reinforcing the paradigm's empirical and theoretical foundations.

Findings

Inflation models match Planck 2013 observations with high precision.

Criticisms by Ijjas, Steinhardt, and Loeb are based on problematic assumptions.

Inflation remains a robust and well-supported theory of the early universe.

Abstract

Models of cosmic inflation posit an early phase of accelerated expansion of the universe, driven by the dynamics of one or more scalar fields in curved spacetime. Though detailed assumptions about fields and couplings vary across models, inflation makes specific, quantitative predictions for several observable quantities, such as the flatness parameter ($\Omega_k = 1 - \Omega$) and the spectral tilt of primordial curvature perturbations ($n_s - 1 = d \ln {\cal P}_{\cal R} / d \ln k$), among others---predictions that match the latest observations from the {\it Planck} satellite to very good precision. In the light of data from {\it Planck} as well as recent theoretical developments in the study of eternal inflation and the multiverse, we address recent criticisms of inflation by Ijjas, Steinhardt, and Loeb. We argue that their conclusions rest on several problematic assumptions, and we conclude that cosmic inflation is on a stronger footing than ever before.