Fluid Interpretation of Cardassian Expansion

Abstract

A fluid interpretation of Cardassian expansion is developed. Here, the Friedmann equation takes the form $H^2=g({\rho }_M)$ where ${\rho }_M$ contains only matter and radiation (no vacuum). The function $g(\rhom)$ returns to the usual $8π\rhom/(3 m_{pl}^2)$ during the early history of the universe, but takes a different form that drives an accelerated expansion after a redshift $z\sim 1$. 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 $ρ_{tot} = {3 m_{pl}^2 \over 8 π} g(\rhom) = \rhom + ρ_K$ containing not only matter density (mass times number density) but also interaction terms ${\rho }_K$. 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 $F\sim r^{\alpha -1}$. 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.

25 pages, 1 figure. Replaced with published version. Title changed in journal

References in corpus (9)

• Accelerated Universe from Gravity Leaking to Extra Dimensions
• A measurement by BOOMERANG of multiple peaks in the angular power spectrum of the cosmic microwave background
• DASI First Results: A Measurement of the Cosmic Microwave Background Angular Power Spectrum
• The 2dF Galaxy Redshift Survey: The bias of galaxies and the density of the Universe
• Cardassian Expansion: a Model in which the Universe is Flat, Matter Dominated, and Accelerating
• Cosmological Parameter Extraction from the First Season of Observations with DASI
• Cosmological implications of the MAXIMA-I high resolution Cosmic Microwave Background anisotropy measurement
• Future Type Ia Supernova Data as Tests of Dark Energy from Modified Friedmann Equations
• Generalized Cardassian Expansion: Models in Which the Universe is Flat, Matter Dominated, and Accelerating

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