# Cardassian expansion: dark energy density from modified Friedmann equations

@article{Freese2005CardassianED,
title={Cardassian expansion: dark energy density from modified Friedmann equations},
author={Katherine Freese},
journal={New Astronomy Reviews},
year={2005},
volume={49},
pages={103-109}
}
• K. Freese
• Published 31 January 2005
• Physics
• New Astronomy Reviews
Abstract The Cardassian universe is a proposed modification to the Friedmann equation in which the universe is flat, matter dominated, and accelerating. In the ordinary Friedmann equation, the right hand side is a linear function of the energy density, H 2  ∼  ρ . Here, instead, the right hand side of the Friedmann equation is a different function of the energy density, H 2  ∼  g ( ρ ). This function returns to ordinary Friedmann at early times, but drives acceleration of the universe at the…
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## References

SHOWING 1-10 OF 18 REFERENCES
Cardassian expansion: a model in which the universe is flat, matter dominated, and accelerating
• Physics
• 2002
Abstract A modification to the Friedmann–Robertson–Walker equation is proposed in which the universe is flat, matter dominated, and accelerating. An additional term, which contains only matter or
Future Type Ia Supernova Data as Tests of Dark Energy from Modified Friedmann Equations
• Physics
• 2003
In the Cardassian model, dark energy density arises from modifications to the Friedmann equation, which becomes H2 = g(ρM), where g(ρM) is a new function of the energy density. The universe is flat,
Cosmological challenges in theories with extra dimensions and remarks on the horizon problem
• Physics
• 1999
We consider the cosmology that results if our observable universe is a 3-brane in a higher dimensional universe. In particular, we focus on the case where our 3-brane is located at the Z{sub 2}
Cosmology with Decaying Vacuum Energy
• Physics
• 1987
Abstract Motivated by recent attempts to solve the cosmological constant problem, we examine the observational consequences of a vacuum energy which decays in time. In both radiation and matter
Fluid Interpretation of Cardassian Expansion
• Physics
• 2003
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
Cosmological imprint of an energy component with general equation of state
• Physics
• 1998
We examine the possibility that a significant component of the energy density of the Universe has an equation of state different from that of matter, radiation, or cosmological constant ({Lambda} ).
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 " z " 0.62. The luminosity distances of these objects are determined by methods that
OBSERVATIONAL EVIDENCE FROM SUPERNOVAE FOR AN ACCELERATING UNIVERSE AND A COSMOLOGICAL CONSTANT
We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 " z " 0.62. The luminosity distances of these objects are determined by methods that