Quintessence, cosmic coincidence, and the cosmological constant

Ivaylo Zlatev, Limin Wang, Paul J. Steinhardt

Research output: Contribution to journalArticlepeer-review

2141 Scopus citations


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 “tracker field,” a form of quintessence, and show how it may explain the coincidence, adding new motivation for the quintessence scenario.

Original languageEnglish (US)
Pages (from-to)896-899
Number of pages4
JournalPhysical review letters
Issue number5
StatePublished - 1999

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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