Cosmic Variance in Cosmology: From Inflation to Today's Largest Scales
Open Access
- Author:
- Deutsch, Anne Sylvie
- Graduate Program:
- Physics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- April 26, 2018
- Committee Members:
- Sarah Elizabeth Shandera, Dissertation Advisor/Co-Advisor
Sarah Elizabeth Shandera, Committee Chair/Co-Chair
Eugenio Bianchi, Committee Member
Kohta Murase, Committee Member
Donghui Jeong, Outside Member - Keywords:
- inflation
cosmology
non-gaussianities
primordial black holes
Sunyaev-Zel'dovitch effect
cosmic variance - Abstract:
- Coupling between sub- and super-Hubble modes can affect the locally observed statistics of our universe. In the context of Quasi-Single Field Inflation, we compute correlation functions and derive the influence of those unobservable modes on observed correlation functions as well as on the inferred cosmological parameters. We start with the case of the power spectrum, and compute the cosmic variance for the spectral index ns and the tensor-to-scalar ratio r. We then study how different classes of diagrams affect the bispectrum in the squeezed limit; in particular, while contact-like diagrams leave the scaling between the long and short modes unchanged, exchange-like diagrams do modify the shape of the bispectrum. We show that the mass of the hidden sector field can hence be biased by an unavoidable cosmic variance that can reach a 1\sigma uncertainty of O(10%) for a weakly non-Gaussian universe. Finally, we go beyond the bispectrum and show how couplings between unobservable and observable modes can affect generic correlation functions with arbitrary order non-derivative self-interactions. The kinetic Sunyaev Zel'dovich (kSZ) and polarized Sunyaev Zel'dovich (pSZ) effects are temperature and polarization anisotropies induced by the scattering of CMB photons from structure in the post-reionization universe, wich can be cross-correlated with tracers of electron distribution to probe remote dipole and quadrupole fields. We first explore the signal arising from pSZ, which is a power asymmetry in the cross-correlation between E or B-mode CMB polarization and the density field. We compare this to the cosmic variance limited noise. By computing the necessary transfer functions and cross-correlations, we compute the signal-to-noise ratio attainable by idealized next generation surveys. We find that a signal-to-noise ratio of ~ 1 - 10 is in principle attainable over a significant range of power multipoles, with the strongest signal coming from the first multipoles in the lowest redshift bins. We then present a set of unbiased minimum variance quadratic estimators for the reconstruction of the dipole and quadrupole fields, and forecast the ability of future CMB experiments and large scale structure surveys to perform this reconstruction in the cosmic variance limit.