Inflationary Cosmological Perturbations of Quantum-Mechanical Origin

TL;DR

This review explains the theory of inflationary cosmological perturbations, emphasizing their quantum-mechanical origin, and compares theoretical predictions with recent CMBR data to constrain inflationary physics.

Contribution

It provides a comprehensive overview of inflationary perturbations, including their quantum origin, power spectrum calculations, and implications for high-energy physics constraints.

Findings

Quantum fluctuations determine perturbation amplitudes

Inflationary power spectra match CMBR observations

Constraints on high-energy physics from cosmological data

Abstract

This review article aims at presenting the theory of inflation. We first describe the background spacetime behavior during the slow-roll phase and analyze how inflation ends and the Universe reheats. Then, we present the theory of cosmological perturbations with special emphasis on their behavior during inflation. In particular, we discuss the quantum-mechanical nature of the fluctuations and show how the uncertainty principle fixes the amplitude of the perturbations. In a next step, we calculate the inflationary power spectra in the slow-roll approximation and compare these theoretical predictions to the recent high accuracy measurements of the Cosmic Microwave Background radiation (CMBR) anisotropy. We show how these data already constrain the underlying inflationary high energy physics. Finally, we conclude with some speculations about the trans-Planckian problem, arguing that this issue could allow us to open a window on physical phenomena which have never been probed so far.