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New Probes of Cosmic Microwave Background Large-Scale Anomalies

Aiola, Simone (2016) New Probes of Cosmic Microwave Background Large-Scale Anomalies. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Fifty years of Cosmic Microwave Background (CMB) data played a crucial role in constraining the parameters of the ΛCDM model, where Dark Energy, Dark Matter, and Inflation are the three most important pillars not yet understood. Inflation prescribes an isotropic universe on large scales, and it generates spatially-correlated density fluctuations over the whole Hubble volume. CMB temperature fluctuations on scales bigger than a degree in the sky, affected by modes on super-horizon scale at the time of recombination, are a clean snapshot of the universe after inflation. In addition, the accelerated expansion of the universe, driven by Dark Energy, leaves a hardly detectable imprint in the large-scale temperature sky at late times. Such fundamental predictions have been tested with current CMB data and found to be in tension with what we expect from our simple ΛCDM model. Is this tension just a random fluke or a fundamental issue with the present model?
In this thesis, we present a new framework to probe the lack of large-scale correlations in the temperature sky using CMB polarization data. Our analysis shows that if a suppression in the CMB polarization correlations is detected, it will provide compelling evidence for new physics on super-horizon scale. To further analyze the statistical properties of the CMB temperature sky, we constrain the degree of statistical anisotropy of the CMB in the context of the observed large-scale dipole power asymmetry. We find evidence for a scale-dependent dipolar modulation at 2.5σ. To isolate late-time signals from the primordial ones, we test the anomalously high Integrated Sachs-Wolfe effect signal generated by superstructures in the universe. We find that the detected signal is in tension with the expectations from ΛCDM at the 2.5σ level, which is somewhat smaller than what has been previously argued. To conclude, we describe the current status of CMB observations on small scales, highlighting the tensions between Planck, WMAP, and SPT temperature data and how the upcoming data release of the ACTpol experiment will contribute to this matter. We provide a description of the current status of the data-analysis pipeline and discuss its ability to recover large-scale modes.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Aiola, Simonesia21@pitt.eduSIA21
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairKosowsky,
Committee MemberFreitas,
Committee MemberNewman,
Committee MemberStarkman,
Committee MemberZentner,
Date: 21 September 2016
Date Type: Publication
Defense Date: 28 April 2016
Approval Date: 21 September 2016
Submission Date: 29 July 2016
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 119
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Cosmology, "Cosmic Microwave Background", "Temperature Anisotropies"
Date Deposited: 21 Sep 2016 20:47
Last Modified: 15 Nov 2016 14:35


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