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 |
ARK |
ark:/87278/s6902n2t |
Setname |
ir_uspace |
ID |
703861 |
Reference URL |
https://collections.lib.utah.edu/ark:/87278/s6902n2t |