Quintessence, Cosmic Coincidence, and the Cosmological Constant
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)
- Department of Physics, Princeton University, Princeton, New Jersey 08540 (United States)
Recent observations suggest that a large fraction of the energy density of the Universe has negative pressure. One explanation is vacuum energy density; another is quintessence in the form of a scalar field slowly evolving down a potential. In either case, a key problem is to explain why the energy density nearly coincides with the matter density today. The densities decrease at different rates as the Universe expands, so coincidence today appears to require that their ratio be set to a specific, infinitesimal value in the early Universe. In this paper, we introduce the notion of a {open_quotes}tracker field,{close_quotes} a form of quintessence, and show how it may explain the coincidence, adding new motivation for the quintessence scenario. {copyright} {ital 1999} {ital The American Physical Society}
- Research Organization:
- Princeton Univ., NJ (United States)
- DOE Contract Number:
- FG02-91ER40671; FG02-95ER40893
- OSTI ID:
- 304264
- Journal Information:
- Physical Review Letters, Vol. 82, Issue 5; Other Information: PBD: Feb 1999
- Country of Publication:
- United States
- Language:
- English
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