Fundamental Physics, the Swampland of Effective Field Theory and Early Universe Cosmology

TL;DR

This paper explores the limitations of effective field theory in early universe cosmology, emphasizing the role of string theory principles in developing nonsingular models and distinguishing between inflationary and alternative scenarios.

Contribution

It discusses criteria for successful early universe models, compares inflation, bouncing, and emergent scenarios, and advocates for string theory insights to go beyond effective field theory.

Findings

Future observations can distinguish between cosmological scenarios.

String theory principles suggest a nonsingular early universe.

Effective field theory may be insufficient for understanding the early universe.

Abstract

Cosmological inflation is not the only early universe scenario consistent with current observational data. I will discuss the criteria for a successful early universe cosmology, compare a couple of the proposed scenarios (inflation, bouncing cosmologies, and the {\it emergent} scenario), focusing on how future observational data will be able to distinguish between them. I will argue that we need to go beyond effective field theory in order to understand the early universe, and that principles of superstring theory will yield a nonsingular cosmology.