Polarisierte Photon- und geflavourte Lepton-Quantenboltzmanngleichungen im frühen Universum
type: CreativeWork
description: Polarisation and Nongaussianity are expected to play a central role in future studies of the cosmic microwave background radiation. Polarisation can be split into a divergence-like E-mode and a curl-like B-mode, of which the later can only be induced by primordial gravitational waves (tensor uctuations of the metric) at leading order. Nongaussiaity is not generated at rst order and is directly proportional to the primordial Nongaussianity of in ation. Thus B-mode polarisation and Nongaussianity constrain in ation models directly. While E-mode polarisation has already been detected and is being observed with increasing precision, B-mode polarisation and Nongaussianity remains elusive. The absence of B-mode polarisation when the primordial uctuations are purely scalar holds, however, only in linear perturbation theory. B-mode polarisation is also generated from scalar sources in second order, which may constitute an important background to the search for primordial gravitational waves. While such an eect would naturally be expected to be relevant at tensor-to-scalar ratios of order 10-5, which is the size of perturbations in the microwave background, only a full second order calculation can tell whether there are no enhancements. For Nongaussianity the situation is analogous: At second order intrinsic Nongaus-sianities are induced to the spectrum, which may be an important background to the primordial Nongaussianity. After the full second-order Boltzmann equations for the cosmological evolution of the polarised radiation distribution have become available, I focused on the novel sources to B-mode polarisation that appear in the second-order collision term, which have not been calculated before. In my PHD thesis I developed a numerical code, which solves the second order Boltzmann hierarchy and calculates the ClBB-spectrum.
abstract: Polarisation and Nongaussianity are expected to play a central role in future studies of the cosmic microwave background radiation. Polarisation can be split into a divergence-like E-mode and a curl-like B-mode, of which the later can only be induced by primordial gravitational waves (tensor uctuations of the metric) at leading order. Nongaussiaity is not generated at rst order and is directly proportional to the primordial Nongaussianity of in ation. Thus B-mode polarisation and Nongaussianity constrain in ation models directly. While E-mode polarisation has already been detected and is being observed with increasing precision, B-mode polarisation and Nongaussianity remains elusive. The absence of B-mode polarisation when the primordial uctuations are purely scalar holds, however, only in linear perturbation theory. B-mode polarisation is also generated from scalar sources in second order, which may constitute an important background to the search for primordial gravitational waves. While such an eect would naturally be expected to be relevant at tensor-to-scalar ratios of order 10-5, which is the size of perturbations in the microwave background, only a full second order calculation can tell whether there are no enhancements. For Nongaussianity the situation is analogous: At second order intrinsic Nongaus-sianities are induced to the spectrum, which may be an important background to the primordial Nongaussianity. After the full second-order Boltzmann equations for the cosmological evolution of the polarised radiation distribution have become available, I focused on the novel sources to B-mode polarisation that appear in the second-order collision term, which have not been calculated before. In my PHD thesis I developed a numerical code, which solves the second order Boltzmann hierarchy and calculates the ClBB-spectrum.
author: Fidler, Christian
language: ger
keywords: info:eu-repo/classification/ddc/530, Kosmische Hintergrundstrahlung, Kosmologie, Boltzmann-Gleichung, Physik, Leptogenese, Baryogenese, Boltzmanngleichungen, cosmology, CMB, leptogenesis, baryogenesis, Boltzmann equations
date published: 2012
date modified: 2026-07-30T19:43:35Z
provider: RWTH Aachen University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Publikationsserver der RWTH Aachen University