**"Three-year Wilkinson Microwave Anisotropy Probe (WMAP)
observations: Implications for cosmology,"** by
D.N. Spergel and 21 others, *Astrophysical
Journal Supplement Series*, 170(2): 377-408, June 2007.

[Authors' affiliations: 13 U.S. and Canadian institutions]

**Abstract:** "A simple cosmological model with only six
parameters (matter density, Omega(m)h(2), baryon density, Omega(b)h(2),
Hubble constant, H-0, amplitude of fluctuations, sigma(8), optical depth,
tau, and a slope for the scalar perturbation spectrum, n(s)) fits not only
the 3 year WMAP temperature and polarization data, but also small-scale CMB
data, light element abundances, large-scale structure observations, and the
supernova luminosity/distance relationship. Using WMAP data only, the
best-fit values for cosmological parameters for the power-law flat Lambda
cold dark matter (Lambda CDM) model are (Omega(m)h(2), Omega(b)h(2), h,
n(s), tau, sigma(s)) = (0.1277(-0.0079)(+0.0080), 0.02229 +/- 0.00073,
0.732(-0.032)(+0.031), 0.958 +/- 0.016, 0.089 +/- 0.030,
0.761(-0.048)(+0.049)). The 3 year data dramatically shrink the allowed
volume in this six-dimensional parameter space. Assuming that the
primordial fluctuations are adiabatic with a power-law spectrum, the WMAP
data alone require dark matter and favor a spectral index that is
significantly less than the Harrison-Zel'dovich-Peebles scale-invariant
spectrum ( n(s) = 1, r = 0). Adding additional data sets improves the
constraints on these components and the spectral slope. For power-law
models, WMAP data alone puts an improved upper limit on the
tensor-to-scalar ratio, r(0.002) < 0.65 ( 95% CL) and the combination of
WMAP and the lensing-normalized SDSS galaxy survey implies r(0.002) <
0.30 ( 95% CL). Models that suppress large-scale power through a running
spectral index or a large-scale cutoff in the power spectrum are a better
fit to the WMAP and small-scale CMB data than the power-law Lambda CDM
model; however, the improvement in the fit to the WMAP data is only
Delta(2)(chi) = 3 for 1 extra degree of freedom. Models with a
running-spectral index are consistent with a higher amplitude of gravity
waves. In a flat universe, the combination of WMAP and the Supernova Legacy
Survey (SNLS) data yields a significant constraint on the equation of state
of the dark energy, w = -0.967(-0.072)(+0.073). If we assume w = -1,
then

the deviations from the critical density, Omega(K), are small: the
combination of WMAP and the SNLS data implies Omega(k) = -0.011 +/- 0.012.
The combination of WMAP 3 year data plus the HST Key Project constraint on
H-0 implies Omega(k) = -0.014 +/- 0.017 and Omega(Lambda) = 0.716 +/-
0.055. Even if we do not include the prior that the universe is flat, by
combining WMAP, large-scale structure, and supernova data, we can still put
a strong constraint on the dark energy equation of state, w = -1.08 +/-
0.12. For a flat universe, the combination of WMAP and other astronomical
data

yield a constraint on the sum of the neutrino masses, Sigma m(nu) < 0.66
eV (95%CL). Consistent with the predictions of simple inflationary
theories, we detect no significant deviations from Gaussianity in the CMB
maps using Minkowski functionals, the bispectrum, trispectrum, and a new
statistic designed to detect large-scale anisotropies in the fluctuations."

This 2007 report from *Astrophysical Journal Supplement Series* was
cited **138 times** in current journal articles
indexed by Clarivate Analytics

during November-December 2008. This latest two-month total, although down a
bit from previous counts, was more than sufficient to extend the report's
status for an eighth consecutive bimonthly period as the most-cited physics
paper published in the last two years. Prior to the most recent tally,
citations to the paper have accrued as follows:

**September-October 2008: ***170 citations*

July-August 2008: *217*

May-June 2008: *148*

March-April 2008: *201*

January-February 2008: *160*

November-December 2007: *116*

September-October 2007: *107*

July-August 2007: *6*

**Total citations to date:
1,263**

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