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Events on Wednesday, April 19th, 2023

Preliminary Exam
Reconstruction of the Radial Velocity Field of the Universe with a joint CMB and Large Scale Structure likelihood analysis
Time: 11:00 am - 6:00 pm
Place: 4274 Chamberlin
Speaker: Yurii Kvasiuk, Physics Graduate Student
Abstract: We develop an optimization-based maximum likelihood approach to analyze the cross-correlation of the Cosmic Microwave Background (CMB) and the Large-Scale Structure (LSS) induced by the kinetic Sunyaev-Zeldovich effect. Our main goal is to reconstruct the radial velocity field of the universe. While the existing quadratic estimator (QE) is statistically optimal for current and near-term experiments, the likelihood can extract more signal-to-noise in the future. Our likelihood formulation has further advantages over the QE, such as the possibility of jointly fitting cosmological and astrophysical parameters. We implement an auto-differentiable likelihood pipeline in JAX, which is computationally tractable for a realistic survey resolution, and evaluate it on the Agora simulation.
Host: Moritz Muenchmeyer
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Department Meeting
Time: 12:15 pm - 1:15 pm
Place: B343 Sterling Hall
Speaker: Mark Eriksson, UW-Madison
Host: Mark Eriksson
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Theory Seminar (High Energy/Cosmology)
New inflationary probes of axion dark matter
Time: 1:00 pm - 2:30 pm
Place: Chamberlin 5280
Speaker: Lingfeng Li, Brown University
Abstract: If a light axion is present during inflation and becomes part of dark matter afterwards, its quantum fluctuations contribute to dark matter isocurvature. In this article, we introduce a whole new suite of cosmological observables for axion isocurvature, which could help test the presence of axions, as well as its coupling to the inflaton and other heavy spectator fields during inflation such as the radial mode of the Peccei-Quinn field. They include correlated clock signals in the curvature and isocurvature spectra, and mixed cosmological-collider non-Gaussianities involving both curvature and isocurvature fluctuations with shapes and running unconstrained by the current data. Taking into account of the existing strong constraints on axion isocurvature fluctuations from the CMB, these novel signals could still be sizable and potentially observable. In some models, the signals, if observed, could even help us significantly narrow down the range of the inflationary Hubble scale, a crucial parameter difficult to be determined in general, independent of the tensor mode.
Host: George Wojcik
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