Cosmic Concordance and Quintessence
We present a comprehensive study of the observational constraints on spatially flat cosmological models containing a mixture of matter and quintessence--a time-varying, spatially inhomogeneous component of the energy density of the universe with negative pressure. Our study also includes the limiting case of a cosmological constant. We classify the observational constraints by redshift: low-redshift constraints include the Hubble parameter, baryon fraction, cluster abundance, the age of the universe, bulk velocity and the shape of the mass power spectrum; intermediate-redshift constraints are due to probes of the redshift-luminosity distance based on Type Ia supernovae, gravitational lensing, the Ly{alpha} forest, and the evolution of large-scale structure; high-redshift constraints are based on measurements of the cosmic microwave background temperature anisotropy. Mindful of systematic errors, we adopt a conservative approach in applying these observational constraints. We determine that the range of quintessence models in which the ratio of the matter density to the critical density is 0.2(less-or-similar sign){omega}{sub m}(less-or-similar sign)0.5, and the effective, density-averaged equation of state is -1{<=}w(less-or-similar sign)-0.2, is consistent with the most reliable, current low-redshift and microwave background observations at the 2 {sigma} level. Factoring in the constraint due to the recent measurements of Type Ia supernovae, the range for the equation of state is reduced to -1{<=}w(less-or-similar sign)-0.4, where this range represents models consistent with each observational constraint at the 2 {sigma} level or better (concordance analysis). A combined maximum likelihood analysis suggests a smaller range, -1{<=}w(less-or-similar sign)-0.6. We find that the best-fit and best-motivated quintessence models lie near {omega}{sub m}{approx_equal}0.33, h(approx =)0.65, and spectral index n{sub s}=1, with an effective equation of state w(approx =)-0.65 for ''tracker'' quintessence and w=-1 for ''creeper'' quintessence. (c) (c) 2000. The American Astronomical Society.
- OSTI ID:
- 20216510
- Journal Information:
- Astrophysical Journal, Vol. 530, Issue 1; Other Information: PBD: 10 Feb 2000; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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