Inflation provides a unified paradigm for understanding the isotropy of the cosmic microwave background (CMB), the flatness problem, and the origin of large-scale structure. Although the physics responsible for inflation is not yet well understood, slow-roll inflation generically makes several predictions: a flat Universe, primordial adiabatic density perturbations, and a stochastic gravity-wav...

The next generation low-frequency radio telescopes may probe cosmological models by means of observations of the cosmic microwave background (CMB). I discuss the prospects for observations of CMB imprints — recombination lines from the epoch of recombination, μ distortions and angular temperature anisotropies — at low frequencies. A future low-frequency radio telescope, like the proposed SKA, m...

Forthcoming CMB experiments will allow us to accurately investigate the power spectrum at very small scales (l > 1000). In this context, we forecast the level of the primary anisotropies, given the actual CMB measurements. The secondary anisotropies generated after matter-radiation decoupling contribute additional power in the tail of the CMB power spectrum. Together with the primary anisotropi...

After cosmological recombination, the primordial hydrogen gas decoupled from the cosmic microwave background (CMB) and fell into the gravitational potential wells of the dark matter. The neutral hydrogen imprinted acoustic oscillations on the pattern of brightness fluctuations due to its redshifted 21cm absorption of the CMB. Unlike CMB temperature fluctuations which probe the power spectrum at...

We revisit the constraint on the primordial helium mass fraction Yp from observations of cosmic microwave background (CMB) alone. By minimizing χ of recent CMB experiments over 6 other cosmological parameters, we obtained rather weak constraints as 0.17 ≤ Yp ≤ 0.52 at 1σ C.L. for a particular data set. We also study the future constraint on cosmological parameters when we take account of the pr...

We present constraints on the cosmological constant λ0 and the density parameter Ω0 from joint constraints from the analyses of gravitational lensing statistics of the Jodrell Bank-VLA Astrometric Survey (JVAS), optical gravitational lens surveys from the literature and CMB anisotropies. This is the first time that quantitative joint constraints involving lensing statistics and CMB anisotropies...

We present a new limit on the cosmological constant based on the absence of correlations between the cosmic microwave background (CMB) and the distribution of distant radio sources. In cosmological constant, cold dark matter ( LambdaCDM) models, such correlations should have been produced via the integrated Sachs-Wolfe effect, assuming that radio sources trace the local ( z approximately 1) mat...

The WMAP first year detection of a high redshift reionization through its imprints on CMB anisotropy T and TE mode angular power spectra calls for a better comprehension of the universe ionization and thermal history after the standard recombination. Different reionization mechanisms predict different signatures in the CMB, both in temperature and polarization anisotropies and in spectral disto...

The Extended Self-Similarity (ESS) of cosmic microwave background (CMB) radiation has been studied using recent data obtained by the space-craft based Wilkinson Microwave Anisotropy Probe. Using the ESS and the high angular scale resolution (arcminutes) of the data it is shown that the CMB temperature space increments exhibit considerable and systematic declination from Gaussianity for high ord...

We present results for the cross-correlation between the WMAP 1st-year cosmic microwave background (CMB) anisotropy data and optical galaxy surveys: the APM and SDSS DR1 catalogs. Our measurement of a positive CMB-galaxy correlation on large angles (θ > 4◦) yields significant detections of the Integrated Sachs-Wolfe (ISW) effect and provides a new estimate of dark-energy in the universe, ΩΛ = 0...