Fluid interpretation of Cardassian expansion

Update Item Information
Publication Type Journal Article
School or College College of Science
Department Physics
Creator Gondolo, Paolo
Other Author Freese, Katherine
Title Fluid interpretation of Cardassian expansion
Date 2003-09
Description A fluid interpretation of Cardassian expansion is developed. Here, the Friedmann equation takes the form H2=g(ρM) where ρM contains only matter and radiation ~no vacuum!. The function g(ρM) returns to the usual 8πM /(3mpl 2 ) during the early history of the Universe, but takes a different form that drives an accelerated expansion after a redshift z~1. One possible interpretation of this function ~and of the right-hand side of Einstein's equations! is that it describes a fluid with total energy density ρtot=(3mpl 2 /8π)g(ρM)=ρM+ρK containing not only matter density (mass times number density) but also interaction terms ρK . These interaction terms give rise to an effective negative pressure which drives cosmological acceleration. These interactions may be due to interacting dark matter, e.g. with a fifth force between particles F~ra-1. Such interactions may be intrinsically four dimensional or may result from higher dimensional physics. A fully relativistic fluid model is developed here, with conservation of energy, momentum, and particle number. A modified Poisson's equation is derived. A study of fluctuations in the early Universe is presented, although a fully relativistic treatment of the perturbations including gauge choice is as yet incomplete.
Type Text
Publisher American Physical Society
Journal Title Physical Review D
Volume 68
Issue 6
First Page 063509-1
Last Page 063509-10
DOI 10.1103/PhysRevD.68.063509
citatation_issn 0556-2821
Subject Cardassian expansion; Friedmann equation
Subject LCSH Expanding universe; Cosmology; Red shift
Language eng
Bibliographic Citation Gondolo, P., & Freese, K. (2003). Fluid interpretation of Cardassian expansion. Physical Review D, 68, 063509-1-063509-10.
Rights Management (c) American Physical Society http://dx.doi.org/10.1103/PhysRevD.68.063509
Format Medium application/pdf
Format Extent 107,775 bytes
Identifier ir-main,9209
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Reference URL https://collections.lib.utah.edu/ark:/87278/s6902n2t