The Quantum State of Inflationary Perturbations

TL;DR

This paper reviews the quantum properties of inflationary perturbations, focusing on the wavefunction, Wigner function, and density matrix, and discusses the implications for the measurement problem in cosmology.

Contribution

It provides a detailed analysis of the quantum state of inflationary perturbations, emphasizing the squeezed state nature and its characterization tools.

Findings

The wavefunction of inflationary perturbations is a strongly squeezed state.

The Wigner function and density matrix effectively characterize the quantum state.

Discussion on the measurement problem and definite outcomes in inflationary cosmology.

Abstract

This article reviews the properties of the quantum state of inflationary perturbations. After a brief description of the inflationary background, the wavefunction of the Mukhanov-Sasaki variable is calculated and shown to be that of a strongly squeezed state. The corresponding Wigner function and density matrix, which are convenient tools to characterize the properties of a quantum state, are also evaluated. Finally, the issue of definite outcomes for inflation is discussed.