The emergence of cosmic repulsion

TL;DR

This paper proposes that the universe's large-scale properties, such as flatness and acceleration, emerge from the cosmic fluid's effective continuum behavior, aligning well with observational data without adjustable parameters.

Contribution

It introduces a novel emergent properties framework for cosmology, explaining key universe features without adjustable parameters and consistent with thermodynamics and observations.

Findings

Universe is spatially flat and accelerating

Dark energy constitutes 75% of total energy density

Model aligns with supernovae Hubble diagram

Abstract

In cosmology based on general relativity, the universe is modeled as a fluid. The transition from the Einstein field equation to its large-scale (cosmological) version is thus analogous to the transition, for a system consisting of a large number of molecules, from the molecular/kinetic description to thermodynamics and hydrodynamics. The cosmic fluid is an effective continuum defined on the cosmological scales (only); for such a continuum, the appearance of new emergent properties should be expected. (Emergence of space-time and gravity is not discussed here.) When these new properties are calculated, the following predictions result: (a) the universe is spatially flat; (b) its expansion is accelerating; (c) dark energy makes up 75% of the total energy density of the universe; (d) the pressure of dark energy is equal and opposite to its density. All of these are in good agreement with the observational data. Also in favor of the present model are the absence of adjustable parameters, and consistency with the second law of thermodynamics. The distance-redshift relation predicted by the model is in good agreement with the Hubble diagram of Type Ia supernovae.