Article

# Dynamics of Cosmological Perturbations in Position Space

Physical Review D (Impact Factor: 4.69). 02/2002; DOI: 10.1103/PhysRevD.65.123008

Source: arXiv

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**ABSTRACT:**This thesis presents the analysis of the clustering of galaxies in the 6dF Galaxy Survey (6dFGS). At large separation scales the baryon acoustic oscillation (BAO) signal is detected which allows to make an absolute distance measurement at $z_{\rm eff} = 0.106$. Such a measurement can be used to constrain the Hubble constant, $H_0 = 67.0\pm3.2\;$km s$^{-1}\;$Mpc$^{-1}$ (4.8% precision). Modelling the 2D galaxy correlation function of 6dFGS, $\xi(r_p,\pi)$, allows a measure of the parameter combination $f(z_{\rm eff})\sigma_8(z_{\rm eff}) = 0.423 \pm 0.055$, where $f \simeq \Omega_m^{\gamma}(z)$ is the growth rate of cosmic structure and $\sigma_8$ is the r.m.s. of matter fluctuations in $8h^{-1}\,$Mpc spheres. Such a measurement allows to test the relationship between matter and gravity on cosmic scales by constraining the growth index of density fluctuations, $\gamma$. The 6dFGS measurement of $f\sigma_8$ combined with WMAP-7, results in $\gamma = 0.547 \pm 0.088$, consistent with the prediction of General Relativity ($\gamma_{\rm GR} \approx 0.55$). The last chapter of this thesis studies the stellar-mass dependence of galaxy clustering in the 6dF Galaxy Survey. Using the Halo Occupation Distribution (HOD) model, this analysis investigates the trend of dark matter halo mass and satellite fraction with stellar mass by measuring the projected correlation function, $w_p(r_p)$. The findings of this analysis are, that the typical halo mass ($M_1$) as well as the satellite power law index ($\alpha$) increase with stellar mass. The 6dFGS results are compared to two different semi-analytic models derived from the Millennium Simulation, as well as weak lensing measurements.03/2013; - [Show abstract] [Hide abstract]

**ABSTRACT:**The effect of the scalar spectral index on inflationary super-Hubble waves is to amplify/damp large wavelengths according to whether the spectrum is red ($n_{s}<1$) or blue ($n_{s}>1$). As a consequence, the large-scale temperature correlation function will unavoidably change sign at some angle if our spectrum is red, while it will always be positive if it is blue. We show that this inflationary filtering property also affects our estimates of the size of the homogeneous patch of the universe through the Grishchuk-Zel'dovich effect. Using the recent quadrupole measurement of ESA's Planck mission, we find that the homogeneous patch of universe is at least 87 times bigger than our visible universe if we accept Planck's best fit value $n_{s}=0.9624$. An independent estimation of the size of the universe could be used to independently constrain $n_{s}$, thus narrowing the space of inflationary models.04/2013; - [Show abstract] [Hide abstract]

**ABSTRACT:**In this thesis, we consider both theoretical and experimental aspects of the cosmic microwave background (CMB) anisotropy for [cursive l] > 500. Part one addresses the process by which the universe first became neutral, its recombination history. The work described here moves closer to achieving the precision needed for upcoming small-scale anisotropy experiments. Part two describes experimental work with the Atacama Cosmology Telescope (ACT), designed to measure these anisotropies, and focuses on its electronics and software, on the site stability, and on calibration and diagnostics. Cosmological recombination occurs when the universe has cooled sufficiently for neutral atomic species to form. The atomic processes in this era determine the evolution of the free electron abundance, which in turn determines the optical depth to Thomson scattering. The Thomson optical depth drops rapidly (cosmologically) as the electrons are captured. The radiation is then decoupled from the matter, and so travels almost unimpeded to us today as the CMB. Studies of the CMB provide a pristine view of this early stage of the universe (at around 300,000 years old), and the statistics of the CMB anisotropy inform a model of the universe which is precise and consistent with cosmological studies of the more recent universe from optical astronomy. The recombination history is the largest known uncertainty in the standard cosmological model for CMB anisotropy formation. Here we investigate the formation of neutral helium during cosmological recombination and find that it is significantly different than was previously understood. We show that several new effects produce a modest (~ 0.5% at [cursive l] = 3000) change in the CMB anisotropy that should be included in the analysis of data from small-scale anisotropy experiments. These small scales contain further information from the primary CMB and from interactions of the CMB with intervening matter as it travels from the recombination era to us today. This information will improve constraints on the spectral slope of primordial perturbations, the baryon density, and possibly dark energy. The methods described in the second half of this thesis are part of the ACT analysis pipeline.06/2008;

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