Dynamics of Cosmological Perturbations in Position Space

Physical Review D (Impact Factor: 4.64). 02/2002; 65(12). DOI: 10.1103/PhysRevD.65.123008
Source: arXiv


We show that the linear dynamics of cosmological perturbations can be described by coupled wave equations, allowing their efficient numerical and, in certain limits, analytical integration directly in position space. The linear evolution of any perturbation can then be analyzed with the Green's function method. Prior to hydrogen recombination, assuming tight coupling between photons and baryons, neglecting neutrino perturbations, and taking isentropic (adiabatic) initial conditions, the obtained Green's functions for all metric, density, and velocity perturbations vanish beyond the acoustic horizon. A localized primordial cosmological perturbation expands as an acoustic wave of photon-baryon density perturbation with narrow spikes at its acoustic wavefronts. These spikes provide one of the main contributions to the cosmic microwave background radiation anisotropy on all experimentally accessible scales. The gravitational interaction between cold dark matter and baryons causes a dip in the observed temperature of the radiation at the center of the initial perturbation. We first model the radiation by a perfect fluid and then extend our analysis to account for finite photon mean free path. The resulting diffusive corrections smear the sharp features in the photon and baryon density Green's functions over the scale of Silk damping. Comment: 19 pages, 5 figures, matches the version to appear in Phys. Rev. D

1 Follower
7 Reads
  • Source
    • ", a powerful analytical treatment by Hu and Sugiyama [43] in Fourier space, another by Bashinsky and Bertschinger [44] in position space, and a review by Hu and Dodelson [45]). It has been confirmed and measured by CMB observations such as the Wilkinson Microwave Anisotropy Probe (WMAP) [46] [47] [48] [49] [50]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper is a review on the observational Hubble parameter data that have gained increasing attention in recent years for their illuminating power on the dark side of the universe: the dark matter, dark energy, and the dark age. Currently, there are two major methods of independent observational measurement, which we summarize as the “differential age method” and the “radial BAO size method.” Starting with fundamental cosmological notions such as the spacetime coordinates in an expanding universe, we present the basic principles behind the two methods. We further review the two methods in greater detail, including the source of errors. We show how the observational data present itself as a useful tool in the study of cosmological models and parameter constraint, and we also discuss several issues associated with their applications. Finally, we point the reader to a future prospect of upcoming observation programs that will lead to some major improvements in the quality of observational data.
    Advances in Astronomy 10/2010; 2010(1687-7969). DOI:10.1155/2010/184284 · 1.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a completely analytic treatment of cosmological fluctua-tions whose wavelength is small enough to come within the horizon well before the energy densities of matter and radiation become equal. This analysis yields a simple formula for the conventional transfer function T (k) at large wave number k, which agrees very well with computer calculations of T (k). It also yields an explicit formula for the microwave background multipole coefficient C ℓ at very large ℓ.
    The Astrophysical Journal 12/2002; 581(2):6-2. DOI:10.1086/344441 · 5.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We consider the image formation for an extremely distant source in an optically dense, homogeneous, and isotropic medium. We show that the angular size of the image would presently be θ0 ≍ 10′, irrespective of the initial redshift z. Parameters of the inhomogeneities capable of producing the observed effect were estimated. We note that this effect should be taken into account for the baryon density fluctuations that were damped according to Silk at the prerecombination epoch. The spot radiation spectrum is shown to be a diluted Planckian spectrum with a dilution factor much larger than unity. We also point out the presence of peculiar tangential polarization in the spot, which reaches several tens of percent at the spot edge. All these observational features clearly distinguish the fluctuations under consideration from the standard fluctuations.
    Astronomy Letters 12/2002; 29(1):6-9. DOI:10.1134/1.1537371 · 1.43 Impact Factor
Show more

Similar Publications


7 Reads
Available from