Can Inflation be Falsified?

TL;DR

This paper argues that the theory of cosmological inflation is indeed falsifiable, with observational data capable of testing both its role in structure formation and initial conditions.

Contribution

It clarifies the falsifiability of inflation by distinguishing its two facets and demonstrating how each can be tested against observational evidence.

Findings

Inflation as a model for structure formation can be excluded by observations.

Initial conditions aspect of inflation can conflict with data.

Both facets of inflation are falsifiable.

Abstract

Despite its central role in modern cosmology, doubts are often expressed as to whether cosmological inflation is really a falsifiable theory. We distinguish two facets of inflation, one as a theory of initial conditions for the hot big bang and the other as a model for the origin of structure in the Universe. We argue that the latter can readily be excluded by observations, and that there are also a number of ways in which the former can find itself in conflict with observational data. Both aspects of the theory are indeed falsifiable.