The intrinsic bispectrum of the Cosmic Microwave Background [PhD thesis]

Abstract

The CMB bispectrum is a potential window on exciting new physics, as it is sensitive to the non-Gaussian features in the primordial fluctuations, the same fluctuations that evolved into today's planets, stars and galaxies. However, this invaluable information is potentially screened, as not all of the observed non-Gaussianity is of primordial origin. Indeed, a bispectrum arises even for perfectly Gaussian initial conditions due to non-linear dynamics, such as CMB photons scattering off free electrons and propagating in an inhomogeneous Universe. In this thesis, I introduce the reader to this intrinsic bispectrum in a pedagogic way, building up from the standard model of cosmology and from cosmological perturbation theory, the tool cosmologists use to unravel the history of the cosmos. In doing so, I introduce $\text{SONG}$, a new and efficient code for solving the second-order Einstein and Boltzmann equations. Next, I move on to answer the crucial question: is the intrinsic bispectrum going to screen the primordial signal in the CMB? Using $\text{SONG}$ I compute the intrinsic bispectrum and shows how its contamination leads to a small bias in the estimates of primordial non-Gaussianity, a great news for the prospect of using CMB data to probe primordial non-Gaussianity.

The thesis' approach is pedagogical, ideal for a PhD student. The SONG code is available at https://github.com/coccoinomane/song/ . Feel free to contact me at [email protected] <mailto:[email protected]> ! UPDATE: Fixed typos & updated references; thesis published in Springer Theses Series at http://www.springer.com/gp/book/9783319218816 <http://www.springer.com/gp/book/9783319218816> ; check out new exciting results with polarisation in arXiv:1406.2981!

References in corpus (32)

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• Tests of the Gravitational Inverse-Square Law below the Dark-Energy Length Scale
• Primordial Non-Gaussianities from Inflation Models
• The Cosmic Linear Anisotropy Solving System (CLASS) I: Overview
• Mission design of LiteBIRD
• Relativistic cosmology and large-scale structure
• The shape of primordial non-Gaussianity and the CMB bispectrum
• The 21cm angular-power spectrum from the dark ages
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• A Concise Introduction to Perturbation Theory in Cosmology
• Non-Gaussianities from Perturbing Recombination
• Gauge invariant Boltzmann equation and the fluid limit
• Impact of polarisation on the intrinsic CMB bispectrum
• Measuring the transition to homogeneity with photometric redshift surveys
• Linear effects of perturbed recombination
• Formulating Weak Lensing from the Boltzmann Equation and Application to Lens-lens Couplings
• CMB Bispectrum from Non-linear Effects during Recombination
• An Introduction into the Theory of Cosmological Structure Formation
• Using galaxy pairs as cosmological tracers
• Testing gravity with non-Gaussianity
• TASI Lectures on Cosmological Perturbations

Cited by in corpus (33)

• General relativistic corrections to $N$-body simulations and the Zel'dovich approximation
• Relativistic Interpretation of Newtonian Simulations for Cosmic Structure Formation
• Relativistic initial conditions for N-body simulations
• The intrinsic B-mode polarisation of the Cosmic Microwave Background
• The Intrinsic Matter Bispectrum in $\Lambda$CDM
• A new approach to cosmological structure formation with massive neutrinos
• A relativistic signature in large-scale structure
• Parameterization of temperature and spectral distortions in future CMB experiments
• Non-Gaussianity of secondary anisotropies from ACTPol and Planck
• The full CMB temperature bispectrum from single-field inflation
• Geodesic "curve"-of-sight formulae for the cosmic microwave background: a unified treatment of redshift, time delay, and lensing
• Formulating Weak Lensing from the Boltzmann Equation and Application to Lens-lens Couplings
• Spectral distortions in the cosmic microwave background polarization
• A new line-of-sight approach to the non-linear Cosmic Microwave Background
• A precise numerical estimation of the magnetic field generated around recombination
• GRAMSES: a new route to general relativistic $N$-body simulations in cosmology. Part II. Initial conditions
• Radiative transport of relativistic species in cosmology
• Effects of non-linearities on magnetic field generation
• CMB spectral distortions as solutions to the Boltzmann equations
• Biases to primordial non-Gaussianity measurements from CMB secondary anisotropies
• Two-point Correlation Functions in Inhomogeneous and Anisotropic Cosmologies
• Unified approach to secondary effects on the CMB B-mode polarization
• Physics of the Cosmic Microwave Background Radiation
• Isocurvature initial conditions for second order Boltzmann solvers
• B-mode Power Spectrum of CMB via Polarized Compton Scattering
• EBWeyl: a Code to Invariantly Characterize Numerical Spacetimes
• From matter to galaxies: General relativistic bias for the one-loop bispectrum
• The parity-odd Intrinsic Bispectrum
• Relativistic second-order initial conditions for simulations of large-scale structure
• Including relativistic and primordial Non-Gaussianity contributions in cosmological simulations by modifying the initial condition
• Relativistic matter bispectrum of cosmic structures on the light cone
• Non-linear effects in early Universe cosmology
• The intrinsic bispectrum of the CMB from isocurvature initial conditions