Constraining physics beyond the cosmological standard model.

摘要

In this thesis we consider cosmological constraints arising from the background expansion history on the effective field theory (EFT) of cosmic acceleration, a theoretical framework that allows for a unified way to classify both models of dark energy and modified gravity within the linear regime. In the Einstein frame, the most general action for the background can be written in terms of a canonical scalar field which is nonminimally coupled to matter. The leading corrections to the action are expressible through a quartic kinetic term, and scalar couplings to a Gauss-Bonnet curvature term and the Einstein tensor. We determine the implications of the terms in this general action for the predicted expansion history in the context of dynamical attractors. We find that each modifies the matter dominated and/or accelerative eras in ways that allow us to place cosmological constraints on them. We present current constraints on the effective action using the latest Type Ia supernovae, cosmic microwave background (CMB), and baryonic acoustic oscillation (BAO) data. This includes the finding that the scalar field EFT with a coupled Gauss-Bonnet term and the data are significantly discrepant.;In addition, we calculate the constraints on dark energy and cosmic modifications to gravity achievable with upcoming CMB surveys sensitive to the Sunyaev-Zel'dovich (SZ) effects. The analysis focuses on using the mean pairwise velocity of clusters as observed through the kinematic SZ effect (kSZ), an approach based on the same methods used for the first detection of the kSZ effect, and includes a detailed derivation and discussion of this statistic's covariance under a variety of different survey assumptions.;The potential of current, "Stage II" (ACTPol + BOSS), and upcoming, "Stage III" (Advanced ACTPol + BOSS), and "Stage IV" (CMB-S4 + DESI), CMB observations are considered, in combination with contemporaneous spectroscopic and photometric galaxy observations. A detailed assessment is made of the sensitivity to the assumed statistical and systematic uncertainties in the optical depth determination, the magnitude and uncertainty in the minimum detectable mass, and the importance of pairwise velocity correlations at small separations, where nonlinear effects can start to arise.;In combination with Stage III constraints on the expansion history, such as those projected by the Dark Energy Task Force, we forecast 5% and 3% for fractional errors on the growth factor, gamma, for Stage III and Stage IV surveys respectively, and 2% constraints on the growth rate, f g, for a Stage IV survey for 0.2 < z < 0.6. The results suggest that kSZ measurements of cluster peculiar velocities, obtained from cross-correlation with upcoming spectroscopic galaxy surveys, could provide robust tests of dark energy and theories of gravity on cosmic scales.;We present the mean pairwise momentum of clusters, as observed through the kSZ effect, as a novel probe of massive neutrinos. We find that kSZ measurements with current and upcoming surveys will provide complementary constraints on the sum of neutrino masses from large scale structure (LSS) and will improve on Planck satellite measurements of the primordial cosmic CMB and CMB lensing. Central to the constraints is a distinctive scale dependency of the kSZ neutrino signature on the mean pairwise momentum of clusters that we do not expect to be mirrored in systematic effects that change the overall amplitude of the signal, like the cluster optical depth. Assuming a minimal LambdaCDM cosmology including massive neutrinos with Planck primordial CMB priors combined with conservative kSZ specifications, we forecast 68% upper limits on the neutrino mass sum of 310, 240, 110 meV for Stage II, Stage III, and Stage IV surveys respectively, compared to the Planck alone forecast of 540 meV. These forecasts include the ability to simultaneously constrain the neutrino mass sum and the mass-averaged optical depth of the cluster sample in each redshift bin. If the averaged optical depth of clusters can be measured with few percent accuracy.;and a lower limiting mass is assumed, the projected kSZ constraints improve further to 100, 85 and 33 meV (Stage II, III and IV). These forecasts represent a conservative estimate of neutrino constraints using cross-correlations of arcminute-resolution CMB measurements and spectroscopic galaxy surveys. More information relevant for neutrino constraints is available from these surveys, such as galaxy clustering, weak lensing, and CMB temperature and polarization.