# 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} }

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…

## 29 Citations

Constraints of gravitational baryo/leptogenesis on Cardassian expansion

- Physics
- 2011

In this paper, proceeding from the relation between the Cardassian model and the accelerated expansion of the universe, adopting a parametric method which does not depend on a precise mechanism for…

Polytropic dark matter flows illuminate dark energy and accelerated expansion

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- 2015

Currently, a large amount of data implies that the matter constituents of the cosmological dark sector might be collisional. An attractive feature of such a possibility is that, it can reconcile dark…

Dark Energy, Hyperbolic Cosecant Cardassian and Virial Collapse for Power-style Cardassian

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- 2009

New work gathers in Chapter 6 and Chapter 7. Tthe Cardassian dynamical equations are introduced generally and logically under GF fluid scenario, together with the flowing process of constructing…

On the cosmological models with matter creation

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The matter creation model of Prigogine–Géhéniau–Gunzig–Nardone is revisited in terms of a redefined creation pressure which does not lead to irreversible adiabatic evolution at constant specific…

More on QCD ghost dark energy

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The difference between the vacuum energy of quantum fields in Minkowski space and in a Friedmann-Robertson-Walker universe might be related to the observed dark energy. The vacuum energy of the…

ACCELERATING UNIVERSE WITH MODIFIED FRIEDMANN EQUATION

- Physics
- 2008

In this paper we propose a specific modification for Friedmann equation which leads during the matter-dominated era to a Cardassian type model, with the usual two undetermined parameters but with an…

FRW viscous modified cosmic Chaplygin gas cosmology in the presence of cosmological constant

- PhysicsInternational Journal of Geometric Methods in Modern Physics
- 2019

In this paper, we study viscous Modified Cosmic Chaplygin Gas (MCCG) in the presence of cosmological constant in flat FRW universe. We assume that bulk viscosity [Formula: see text] and cosmological…

Exponential Cardassian universe

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- 2006

Abstract The expectation of explaining cosmological observations without requiring new energy sources is forsooth worthy of investigation. In this Letter, a new kind of Cardassian models, called…

Perturbations of Dark Matter Gravity

- Physics
- 2009

Until recently the study of the gravitational field of dark matter was primarily concerned with its local effects on the motion of stars in galaxies and galaxy clusters. On the other hand, the WMAP…

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