Download or read book Constraining Cosmological Parameters with Gravitational Lensing of the Cosmic Microwave Background written by Gabrielle Simard and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The cosmic microwave background (CMB) anisotropies are a direct probe of early Universe physics. They also carry information about the late Universe through different secondary effects, including gravitational lensing. Propagating away from the last scattering surface, the primary CMB photons are deflected by the intervening large-scale structure, creating slight distortions in the CMB radiation temperature and polarization patterns that can be detected statistically. In this thesis, we present constraints on the parameters describing our Universe on cosmological scales obtained with the use of CMB gravitational lensing measurements. We begin with a description of the current cosmological model and follow with a review of gravitational lensing effects on the CMB observables.We then present bounds on cosmological parameters set by the lensing power spectrum estimated from a combined SPT+Planck CMB temperature map on the SPT-SZ 2500 square-degrees patch of sky.Adding lensing information to primary CMB data helps tightening constraints on cosmological parameters affecting late-time growth, such as the matter fluctuation amplitude today, the spatial curvature and the sum of neutrino masses.Measurements of the CMB polarization sourced in the early Universe are hindered by the additional polarization created by the gravitational lensing deflections; this contaminating lensing signal can be estimated and removed. We discuss projected constraints on the scale-dependence of the primordial CMB polarization signal assuming that the lensing induced contamination can be subtracted through different scenarios." --

Download or read book Constraining Neutrino Masses with Gravitational Lensing of the Cosmic Microwave Background written by Gabrielle Simard and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "By deflecting photon trajectories, weak gravitational lensing shifts cosmic microwave background (CMB) anisotropies. The power spectrum of the lensing deflection field carries significant information about structure formation.The growth of structure in the universe is affected by neutrinos, confirmed to have a non-zero total mass by the latest neutrino flavor oscillation experiments. Using statistical estimators of the deflection field, we have evaluated through a Fisher forecast the capacity of present and near future CMB experiments SPT-SZ, SPTpol and Planck to constrain cosmological parameters and the total neutrino mass. We find that including lensing information in the forecast allows the SPT-SZ, SPTpol and Planck combined constraint to improve from 0.32 eV to 0.089 eV. The 1-sigma constraint on the sum of neutrino masses from Planck alone improves from 0.39 eV to 0.11 eV when including lensing. Furthermore, we conclude that a greater SPTpol survey area is favored in order to maximize the SPT-SZ, SPTpol and Planck combined constraint on the total neutrino mass. " --

Download or read book Probing the New Cosmology written by Andrew Zentner and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Improvements in obserational techniques have transformed cosmology into a field inundated with ever-expanding, high-quality data sets and driven cosmology toward a standard model where the classic cosmological parameters are accurately measured. I briefly discuss some of the methods used to determine cosmological parameters, particularly primordial nucleosynthesis, the magnitude-redshift relation of supernovae, and cosmic microwave background anisotropy. I demonstrate how cosmological data can be used to complement particle physics and constrain extensions to the Standard Model. Specifically, I present bounds on light particle species and the properties of unstable, weakly-interacting, massive particles. Despite the myriad successes of the emerging cosmological model, unanswered questions linger. Numerical simulations of structure formation predict galactic central densities that are considerably higher than observed. They also reveal hundreds of satellites orbiting Milky Way-like galaxies while the Milky Way has only eleven known satellites within 300kpc. I explore the possibility that these conundrums may have a common remedy in the form of the power spectrum of initial density fluctuations that seed structure growth. To address the substructure issue, I develop a semi-analytic method that suffers from no inherent resolution limits and can therefore be used to complement numerical simulations. I find that tilted primordial power spectra and spectra with running tilts provide for an intriguing possibility. In these models, the amplitude of initial fluctuations can be normalized against the cosmic microwave background measurements on large scales. Yet, the reduction in small-scale power brings galactic central densities down to acceptable levels and allows for the Milky Way satellite population to be accounted for without invoking differential feedback mechanisms. Furthermore, substructure mass fractions are not significantly altered in these models so probes of substructure via gravitational lensing do not disfavor them. The primordial fluctuations are thought to be generated during an early epoch of inflation and one implication is that galaxy properties may convey information about inflation. I also address alternative proposals, such as warm dark matter and broken scale-invariant inflation, in light of lensing probes of substructure and find these models to be disfavored. I close with a few words on refining the model and alternative applications.

Download or read book Constraints on Cosmological Parameters from Weak Lensing and the Cosmic Microwave Background written by Ole Lund Frederiksen and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fundamental Parameters in Cosmology written by J. Thanh Van Tran and published by Atlantica Séguier Frontières. This book was released on 1998 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Constraining Cosmological Models with Cosmic Microwave Background Fluctuations from the Late Universe written by Tommaso Giannantonio and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book One Hundred Years Of General Relativity From Genesis And Empirical Foundations To Gravitational Waves Cosmology And Quantum Gravity Volume 2 written by Wei-tou Ni and published by World Scientific. This book was released on 2017-05-26 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this two-volume title is to give a comprehensive review of one hundred years of development of general relativity and its scientific influences. This unique title provides a broad introduction and review to the fascinating and profound subject of general relativity, its historical development, its important theoretical consequences, gravitational wave detection and applications to astrophysics and cosmology. The series focuses on five aspects of the theory: The first three topics are covered in Volume 1 and the remaining two are covered in Volume 2. While this is a two-volume title, it is designed so that each volume can be a standalone reference volume for the related topic.

Download or read book Extracting Cosmological Information from Small Scales in Weak Gravitational Lensing Data written by Jose Manuel Zorrilla Matilla and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Second, we propose a novel measurement, that of the temperature dipole induced on the cosmic microwave background induced by the rotation of ionized gas around galaxies, as an additional observation to help constrain the distribution of baryonic matter on the smallest scales probed by WL experiments. The uncertainty in this distribution is a major theoretical systematic for future surveys. Third, we show how deep neural networks can be used to map pixel-level data into the cosmological parameters of interest, by-passing the previous compression step of measuring pre-designed statistics. We provide the first (simulation-based) credible contours based on neural networks applied to weak lensing data, and discuss how to interpret these models.

Download or read book Forecasting and Extracting Cosmological Information from Galaxy Cluster Peculiar Velocities written by Alan Campbell Peel and published by . This book was released on 2003 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cosmic Microwave Background Polarization Science and Optical Design of the POLARBEAR and Simons Array Experiments written by Frederick Takayuki Matsuda and published by . This book was released on 2017 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cosmic microwave background (CMB) radiation contains great amounts of information that allow for studying the physics of the early universe through constraining cosmological parameters in the standard [Lambda]CDM model. The CMB temperature signal has been measured to high precision, but measuring the CMB polarization signal is still in its early stages. The theoretically small primordial CMB polarization B-mode signal has not yet been measured, but has principle importance in that its existence would be strong evidence of inflation. This measurement allows one to probe the earliest state of the universe at energy scales of 10^16 GeV thought to be near the Grand Unified Theory scale. The B-mode signal arising from weak gravitational lensing by large scale structures provides information about the matter composition of the universe and puts strong constraints on the sum of the neutrino masses. This dissertation discusses the optical design, instrumentation, data analysis, and first season science results of the POLARBEAR experiment, a CMB polarization telescope aimed to measure the B-mode signal. The results show the first evidence of non-zero lensing B-modes at sub-degree angular scales on the sky. The development and measurement results of the Fourier transform spectrometer calibration instrument used to characterize the spectral response of the POLARBEAR detectors are also described. The optical design development and systematic studies for the Simons Array, the next generation installment of the experiment, are described as well. The cross polarization effect of Mizuguchi-Dragone breaking due to a prime focus half-wave plate, and the optical redesign of the Simons Array re-imaging optics for increased optical performance at higher frequencies were studied in detail. The Simons Array is planned to fully deploy in 2018 to further study the CMB with enhanced sensitivity.

Download or read book Constraining Gravitational and Cosmological Parameters with Astrophysical Data written by Yi Mao (Ph. D.) and published by . This book was released on 2008 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt: We use astrophysical data to shed light on fundamental physics by constraining parametrized theoretical cosmological and gravitational models. Gravitational parameters are those constants that parametrize possible departures from Einstein's general theory of relativity (GR). We develop a general framework to describe torsion in the space time around the Earth, and show that certain observables of the Gravity Probe B (GPB) experiment can be computed in this framework. We examine a toy model showing how a specific theory in this framework can be constrained by GPB data. We also search for viable theories of gravity where the Ricci scalar R in the Lagrangian is replaced by an arbitrary function f(R). Making use of the equivalence between such theories and scalar-tensor gravity, we find that models can be made consistent with solar system constraints either by giving the scalar a high mass or by exploiting the so-called Chameleon Effect. We explore observational constraints from the late-time cosmic acceleration, big bang nucleosynthesis and inflation. Cosmology can successfully describe the evolution of our universe using six or more adjustable cosmological parameters. There is growing interest in using 3-dimensional neutral hydrogen mapping with the redshifted 21 cm line as a cosmological probe. We quantify how the precision with which cosmological parameters can be measured depends on a broad range of assumptions. We present an accurate and robust method for measuring cosmological parameters that exploits the fact that the ionization power spectra are rather smooth functions that can be accurately fit by 7 phenomenological parameters. We find that a future square kilometer array optimized for 21 cm tomography could have great potential, improving the sensitivity to spatial curvature and neutrino masses by up to two orders of magnitude, to k 0.0002 and m 0.007eV, and giving a 4s detection of the spectral index running predicted by the simplest inflation models.

Download or read book Gravitational wave Cosmology Across 29 Decades in Frequency written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Studies Into the Averaging Problem written by Tharake S. Wijenayake and published by . This book was released on 2016 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the tremendous improvement in the precision of available astrophysical data in the recent past, it becomes increasingly important to examine some of the underlying assumptions behind the standard model of cosmology and take into consideration nonlinear and relativistic corrections which may affect it at percent precision level. Due to its mathematical rigor and fully covariant and exact nature, Zalaletdinov's macroscopic gravity (MG) is arguably one of the most promising frameworks to explore nonlinearities due to inhomogeneities in the real Universe. We study the application of MG to precision cosmology, focusing on developing a self-consistent cosmology model built on the averaging framework that adequately describes the large-scale Universe and can be used to study real data sets. We first implement an algorithmic procedure using computer algebra systems to explore new exact solutions to the MG field equations. After validating the process with an existing isotropic solution, we derive a new homogeneous, anisotropic and exact solution. Next, we use the simplest (and currently only) solvable homogeneous and isotropic model of MG and obtain an observable function for cosmological expansion using some reasonable assumptions on light propagation. We find that the principal modification to the angular diameter distance is through the change in the expansion history. We then linearize the MG field equations and derive a framework that contains large-scale structure, but the small scale inhomogeneities have been smoothed out and encapsulated into an additional cosmological parameter representing the averaging effect. We derive an expression for the evolution of the density contrast and peculiar velocities and integrate them to study the growth rate of large-scale structure. We find that increasing the magnitude of the averaging term leads to enhanced growth at late times. Thus, for the same matter content, the growth rate of large scale structure in the MG model is stronger than that of the standard model. Finally, we constrain the MG model using Cosmic Microwave Background temperature anisotropy data, the distance to supernovae data, the galaxy power spectrum, the weak lensing tomography shear-shear cross-correlations and the baryonic acoustic oscillations. We find that for this model the averaging density parameter is very small and does not cause any significant shift in the other cosmological parameters. However, it can lead to increased errors on some cosmological parameters such as the Hubble constant and the amplitude of the linear matter spectrum at the scale of 8h-1Mpc. Further studies are needed to explore other solutions and models of MG as well as their effects on precision cosmology.

Download or read book Highlights in Gravitation and Cosmology written by B. R. Iyer and published by CUP Archive. This book was released on 1988 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Constraining the Thermal History of the Universe with the Cosmic Microwave Background written by Silvia Galli and published by . This book was released on 2011 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: The excellent agreement between the Standard Model of Cosmology and the recent measurements of the Cosmic Microwave Background (CMB) permits to constrain a wide range of physical processes. In particular, in this thesis we exploit the remarkable agreement between the theoretical description of the recombination process, occurring at z~1000, and the CMB data to severely constrain phenomena that affect the evolution of the thermal history of the universe. This contributes answering some important issues still unsolved in the standard model of cosmology. We first address the problem of the nature of dark matter. An extra energy injection due to dark matter annihilation during the epoch of recombination would affect the shape of the CMB power spectra. This allows to constrain dark matter properties using the CMB. The second question regards the validity of conventional physics to describe the Universe. New fundamental theories might predict the space-time variation of fundamental 'constants'. In this thesis we test the constancy of the gravitational constant and of the fine structure constant using the CMB. The third question concerns the characteristics (and in particular, the evolution) of dark energy. The information that can be extracted from the CMB is limited, making necessary the use of complementary probes that can break degeneracies between parameters. This is the case for the evolution of the dark energy equation of state with time, that the CMB can only weakly constrain. We thus show how the observation of clusters of galaxies combined with CMB can be a powerful tool to constrain dark energy.

Download or read book Constraining Cosmology with Weak Gravitational Lensing written by Kellen J. Murphy and published by . This book was released on 2013 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Illuminating the Background written by Nathan James Miller and published by . This book was released on 2012 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cosmic microwave background provides a wealth of information about the origin and history of the universe. The statistics of the anisotropy and the polarization of the cosmic microwave background, among other things, can tell us about the distribution of matter, the redshift of reionization, and the nature of the primordial fluctuations. From the lensing of cosmic microwave background due to intervening matter, we can extract information about neutrinos and the equation of state of dark energy. A measurement of the large angular scale B-mode polarization has been called the "smoking gun'' of inflation, a theory that describes a possible early rapid expansion of the universe. The focus of current experiments is to measure this B-mode polarization, while several experiments, such as POLARBEAR, are also looking to measure the lensing of the cosmic microwave background. This dissertation will discuss several different topics in cosmic microwave background polarization research. I will make predictions for future experiments and I will also show analysis for two current experiments, POLARBEAR and BICEP. I will show how beam systematics affect the measurement of cosmological parameters and how well we must limit these systematics in order to get unbiased constraints on cosmological parameters for future experiments. I will discuss a novel way of using the temperature-polarization cross-correlation to constrain the amount of inflationary gravitational waves. Through Markov Chain Monte Carlo methods, I will determine how well future experiments will be able to constrain the neutrino masses and their degeneracy parameters. I will show results from current data analysis and calibration being done on the Cedar Flat deployment for the POLARBEAR experiment which is currently being constructed in the Atacama desert in Chile. Finally, I will analyze the claim of detection of cosmological birefringence in the BICEP data and show that there is reason to believe it is due to systematic effects in the data.