This open access book offers a concise yet pedagogic introduction to the theory of cosmological inflation and the early epochs that follow it. Inflation explains how the seeds for density perturbations could have formed during a period of exponential expansion. Apart from density perturbations, also so-called tensor perturbations are generated, which may be observed as gravitational waves. Starting from the Einstein equations of general relativity, the formalism is developed through explicit computations and a careful explanation of both the mathematics and the physics involved, paying special attention to general-relativistic gauge invariance. For technically cumbersome steps, examples of numerical and symbolic computer scripts are provided. We also discuss the issue of thermalization, by which a part of the energy density driving the exponential expansion can eventually be converted into the conventional hot big bang. The book is primarily aimed at graduate students of theoretical high-energy physics, but can serve as a self-contained introduction to inflation also for advanced undergraduate students, or for professional scientists.

This book is open access, which means that you have free and unlimited access Provides a pedagogic and self-contained exposition of the inflationary paradigm Demonstrates how early inflation can go over to the subsequent hot big bang Explains how various gravitational wave signatures originate during these processes

Autorentext

Mikko Laine had PhD 1994 in Helsinki, was postdoc in Helsinki, Heidelberg, and CERN, and professor of theoretical physics in Bielefeld 2003-2012 and Bern 2012-today. He has published over 150 scientific articles, mostly on thermal field theory and particle cosmology. Mikko Laine is a co-author of the book "Basics of thermal field theory" (Springer, 2016). Simona Procacci had PhD 2023 in Bern, and a postdoc in Geneva 2023-today. She has published close to 10 scientific articles on inflationary cosmology, cosmological phase transitions, and gravitational wave physics. Simona Procacci got the faculty prize for the best PhD thesis in physics at the University of Bern in 2023, which served as an inspiration for this book.

Inhalt

Einstein equations and the cosmological background solution.- Observable signatures beyond the background solution.- Evolution equations for first order perturbations.- Gauge transformations and different gauges.- Solution with vacuum initial conditions in de Sitter spacetime.- Solution for a general cold inflation scenario.- Evolution equations in the presence of a thermalizing plasma.- What happens when the modes exit the Hubble horizon?.- What happens when the modes re enter the Hubble horizon?.- Gravitational-wave probes of the inflationary period.