Inflation and String Cosmology

TL;DR

This paper reviews the development of inflationary cosmology, discusses quantum fluctuations and observational data, and evaluates alternative scenarios like ekpyrosis, highlighting the current status and challenges of inflation theory.

Contribution

It provides a comprehensive overview of inflationary models, recent observational insights, and critically assesses the viability of alternative scenarios such as ekpyrosis.

Findings

Inflationary models have evolved from Starobinsky to chaotic inflation.

Quantum fluctuations and density perturbations are key to structure formation.

Ekpyrotic scenario currently lacks viability as an alternative to inflation.

Abstract

Inflationary theory is already 20 years old, and it is impossible to describe all of its versions and implications in a short talk. I will concentrate on several subjects which I believe to be most important. First of all, I will give a brief review of the first versions of inflationary theory, from Starobinsky model to new inflation. Then I will describe chaotic inflation, the theory of quantum fluctuations and density perturbations, the theory of eternal inflation, and recent observational data. In the second part of the talk I will discuss the recently proposed ekpyrotic scenario and argue that in its present form it does not provide a viable alternative to inflation.