Cardassian expansion: Dark energy density from modified Friedmann equations
Jan, 20057 pages
Part of Proceedings, 6th UCLA Symposium on Sources and Detection of Dark Matter and Dark Energy in the Universe : Marina del Rey, CA, USA, February 18-20, 2004, 103-109
Published in:
- New Astron.Rev. 49 (2005) 103-109
Contribution to:
e-Print:
- astro-ph/0501675 [astro-ph]
Report number:
- MCTP-04-27
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Abstract: (arXiv)
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, . Here, instead, the right hand side of the Friedmann equation is a different function of the energy density, . This function returns to ordinary Friedmann at early times, but drives acceleration of the universe at the current epoch. The only ingredients in this universe are matter and radiation: in particular, there is NO vacuum contribution. The new term required may arise, e.g., as a consequence of our observable universe living as a 3-dimensional brane in a higher dimensional universe. A second possible interpretation of Cardassian expansion is developed, in which we treat the modified Friedman equations as due to a fluid, in which the energy density has new contributions with negative pressure (possibly due to dark matter with self-interactions). Predictions are shown for observational tests of generalized Cardassian models in future supernova surveys.- Friedman model
- dark energy: density
- astrophysics: acceleration
- fluid
- pressure
- supernova
- quintessence
- numerical calculations: interpretation of experiments
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