Neutrinos as a probe of curvature

TL;DR

This paper investigates how neutrinos influence tensor mode perturbations in different curved spacetimes, highlighting their potential to help determine the universe's spatial curvature.

Contribution

It analyzes the damping effect of neutrinos on tensor modes across various curvature scenarios, emphasizing their role in probing the universe's geometry.

Findings

Neutrinos cause damping of tensor modes during inflation.

Maximum difference observed between closed and open universes in matter era.

Neutrinos can serve as probes for the universe's spatial curvature.

Abstract

Neutrinos, as the anisotropic stress tensor, have a damping effect on the tensor mode perturbation from inflation to the $ \Lambda$ dominated era. First, we study the squared amplitude reduction for the wavelength entering the horizon during radiation and matter-dominated phases in the negatively curved de Sitter spacetime. Then, by comparing with other spatial spacetimes, $ K=0 $ and $K=1$, the highest difference between closed and open cases is seen in the matter-dominated era. Thus, neutrinos can be added as another candidate for determining the nature of space-time.