Origin of structure: Statistical characterization of the primordial density fluctuations and the collapse of the wave function

TL;DR

This paper explores how spontaneous quantum state reduction models alter the statistical predictions of primordial density fluctuations, providing new insights into the origin of cosmic inhomogeneities beyond traditional inflationary theories.

Contribution

It introduces a novel approach to primordial perturbations based on spontaneous quantum collapse, contrasting with conventional quantum-to-classical transition models.

Findings

Spectrum and bispectrum predictions differ from traditional models.

Statistical features require different treatment under collapse models.

Results suggest alternative mechanisms for the origin of cosmic inhomogeneities.

Abstract

The statistical properties of the primordial density perturbations has been considered in the past decade as a powerful probe of the physical processes taking place in the early universe. Within the inflationary paradigm, the properties of the bispectrum are one of the keys that serves to discriminate among competing scenarios concerning the details of the origin of cosmological perturbations. However, all of the scenarios, based on the conventional approach to the so-called "quantum-to-classical transition" during inflation, lack the ability to point out the precise physical mechanism responsible for generating the inhomogeneity and anisotropy of our universe starting from and exactly homogeneous and isotropic vacuum state associated with the early inflationary regime. In past works, we have shown that the proposals involving a spontaneous dynamical reduction of the quantum state provide plausible explanations for the birth of said primordial inhomogeneities and anisotropies. In the present manuscript we show that, when considering within the context of such proposals, the characterization of the spectrum and bispectrum turn out to be quite different from those found in the traditional approach, and in particular, some of the statistical features, must be treated in a different way leading to some rather different conclusions.