# 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… Expand

#### 29 Citations

Constraints of gravitational baryo/leptogenesis on Cardassian expansion

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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… Expand

Polytropic dark matter flows illuminate dark energy and accelerated expansion

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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… Expand

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

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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… Expand

ACCELERATING UNIVERSE WITH MODIFIED FRIEDMANN EQUATION

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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… Expand

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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… Expand

Exponential Cardassian universe

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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… Expand

Cosmic acceleration from a single fluid description

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We here propose a new class of barotropic factor for matter, motivated by properties of isotropic deformations of crystalline solids. Our approach is dubbed Anton-Schmidt's equation of state and… Expand

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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… Expand

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