Quintessence, cosmological horizons, and self-tuning
Abstract
We point out that quintessence with an exponential potential V0 exp(-betaQ/31/2Mp) can account for the present observed acceleration of the universe, without necessarily leading to eternal acceleration. This occurs for 2.4 < beta < 2.8. Thus a cosmological horizon, which is supposed to be problematic within the context of string theory, can be avoided. We argue that this class of models is not particularly fine-tuned. We further examine this question in the context of a modified Friedmann equation, H2proptorho+p, which is suggested by higher dimensional self-tuning approaches to the cosmological constant problem. It is shown that the self-tuning case can also be consistent with observations, if 1.8 < beta < 2.4 (where the potential is now parametrized as V0exp (-betaQ/2Mp)). Future observations of high-z supernovae will be able to test whether beta lies in the desired range.
- Publication:
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Journal of High Energy Physics
- Pub Date:
- August 2001
- DOI:
- 10.1088/1126-6708/2001/08/035
- arXiv:
- arXiv:hep-ph/0105251
- Bibcode:
- 2001JHEP...08..035C
- Keywords:
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- High Energy Physics - Phenomenology;
- Astrophysics;
- High Energy Physics - Theory
- E-Print:
- 13 pp., 5 figures