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Title: Explaining the dark energy, baryon and dark matter coincidence via domain-dependent random densities

Abstract

The dark energy, dark matter and baryon densities in the Universe are observed to be similar, with a factor of no more than 20 between the largest and smallest densities. We show that this coincidence can be understood via superhorizon domains of randomly varying densities when the baryon density at initial collapse of galaxy-forming perturbations is determined by anthropic selection. The baryon and dark matter densities are assumed to be dependent on random variables θ{sub d} and θ{sub b} according to ρ{sub dm}∝θ{sub d}{sup α} and ρ{sub b}∝θ{sub b}{sup β}, while the effectively constant dark energy density is dependent upon a random variable φ{sub Q} according to ρ{sub Q}∝φ{sub Q}{sup n}. The ratio of the baryon density to the dark energy density at initial collapse, r{sub Q}, and the baryon-to-dark matter ratio, r, are then determined purely statistically, with no dependence on the anthropically-preferred baryon density. We compute the probability distribution for r{sub Q} and r and show that the observed values of r{sub Q} and r can be naturally understood within this framework. In particular, for the case α = 2, β = 1 and n = 4, which can be physically realized via a combination of axion darkmore » matter, Affleck-Dine baryogenesis and frozen quintessence with a φ{sub Q}{sup 4} potential, the range of r{sub Q} and r which corresponds to the observed Universe is a quite natural, with a probability which is broadly similar to other ranges of r{sub Q} and r.« less

Authors:
 [1]
  1. Lancaster-Manchester-Sheffield Consortium for Fundamental Physics, Cosmology and Astroparticle Physics Group, Dept. of Physics, University of Lancaster, Lancaster LA1 4YB (United Kingdom)
Publication Date:
OSTI Identifier:
22282872
Resource Type:
Journal Article
Journal Name:
Journal of Cosmology and Astroparticle Physics
Additional Journal Information:
Journal Volume: 2013; Journal Issue: 05; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1475-7516
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; BARYONS; COSMOLOGY; DENSITY; GALAXIES; NONLUMINOUS MATTER; PERTURBATION THEORY; POTENTIALS; PROBABILITY; RANDOMNESS; UNIVERSE

Citation Formats

McDonald, John. Explaining the dark energy, baryon and dark matter coincidence via domain-dependent random densities. United States: N. p., 2013. Web. doi:10.1088/1475-7516/2013/05/019.
McDonald, John. Explaining the dark energy, baryon and dark matter coincidence via domain-dependent random densities. United States. doi:10.1088/1475-7516/2013/05/019.
McDonald, John. Wed . "Explaining the dark energy, baryon and dark matter coincidence via domain-dependent random densities". United States. doi:10.1088/1475-7516/2013/05/019.
@article{osti_22282872,
title = {Explaining the dark energy, baryon and dark matter coincidence via domain-dependent random densities},
author = {McDonald, John},
abstractNote = {The dark energy, dark matter and baryon densities in the Universe are observed to be similar, with a factor of no more than 20 between the largest and smallest densities. We show that this coincidence can be understood via superhorizon domains of randomly varying densities when the baryon density at initial collapse of galaxy-forming perturbations is determined by anthropic selection. The baryon and dark matter densities are assumed to be dependent on random variables θ{sub d} and θ{sub b} according to ρ{sub dm}∝θ{sub d}{sup α} and ρ{sub b}∝θ{sub b}{sup β}, while the effectively constant dark energy density is dependent upon a random variable φ{sub Q} according to ρ{sub Q}∝φ{sub Q}{sup n}. The ratio of the baryon density to the dark energy density at initial collapse, r{sub Q}, and the baryon-to-dark matter ratio, r, are then determined purely statistically, with no dependence on the anthropically-preferred baryon density. We compute the probability distribution for r{sub Q} and r and show that the observed values of r{sub Q} and r can be naturally understood within this framework. In particular, for the case α = 2, β = 1 and n = 4, which can be physically realized via a combination of axion dark matter, Affleck-Dine baryogenesis and frozen quintessence with a φ{sub Q}{sup 4} potential, the range of r{sub Q} and r which corresponds to the observed Universe is a quite natural, with a probability which is broadly similar to other ranges of r{sub Q} and r.},
doi = {10.1088/1475-7516/2013/05/019},
journal = {Journal of Cosmology and Astroparticle Physics},
issn = {1475-7516},
number = 05,
volume = 2013,
place = {United States},
year = {2013},
month = {5}
}