A quantum state for the late Universe

TL;DR

This paper proposes a quantum model of the universe where the de Sitter geometry arises from a scalar field, suggesting quantum effects could influence galactic dynamics and measurements of the Hubble constant.

Contribution

It introduces a toy quantum model linking de Sitter space to scalar field coherent states, providing insights into quantum effects on cosmological observations.

Findings

Modified Newtonian dynamics at galactic scales

Different measured values of the Hubble parameter

Quantum state normalizability influences cosmological parameters

Abstract

We consider the quantum description of a toy model universe in which the Schwarzschild-de Sitter geometry emerges from the coherent state of a massless scalar field. Although highly idealised, this simple model allows us to find clear hints supporting the conclusion that the reaction of the de Sitter background to the presence of matter sources induces i) a modified Newtonian dynamics at galactic scales and ii) different values measured for the present Hubble parameter. Both effects stem from the conditions required to have a normalisable quantum state.