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Events on Friday, March 25th, 2022

Wisconsin Quantum Institute
HQAN Quantum Research Colloquium
Time: 9:00 am
Place: 4274 Chamberlin
Speaker: Hannes Bernien and Kevin Singh (UChicago), Alex Levchenko (UW-Madison)
Abstract: Join the hybrid meeting for HQAN's biweekly research colloquium. Coffee and pastries will be provided.
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Theory Seminar (High Energy/Cosmology)
Wormholes and Saddles in Axion Gravity
Time: 1:00 pm
Place: Chamberlin 5280
Speaker: Gregory Loges, UW Madison
Abstract: The saddle-point approximation often used to make sense of path integrals is especially subtle when gravity is dynamical, most notably because of the conformal factor problem which renders the action unbounded below. In this talk I will discuss two aspects of saddle points in axion gravity, making use of the dual description in terms of a 3-form flux: (i) how Picard-Lefschetz theory can be used to identify in a democratic way which Lorentzian, complex and Euclidean saddle points contribute to Lorentzian path integrals, and (ii) the perturbative stability of the Giddings-Strominger Euclidean wormhole. Based on [2203.01956] with Gary Shiu and Nidhi Sudhir.
Host: George Wojcik
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Physics Department Colloquium
Exploring cosmology with the South Pole Telescope
Time: 3:30 pm
Place: 2103 Chamberlin Hall
Speaker: Amy Bender, Argonne National Laboratory
Abstract: Observations of the cosmic microwave background (CMB) probe a diverse set of fundamental physics in both the early and late universe. CMB measurements are a cornerstone of our now exceptionally precise Lambda-CDM model of cosmology, however, many questions remain. Did an inflationary epoch occur a fraction of a second after the Big Bang? What is the nature of dark energy? Is the Hubble constant controversy new physics or simply measurement systematics? I will describe the SPT-3G receiver that is currently installed on the South Pole Telescope and how it is measuring the CMB to answer these questions. Now starting the fourth year of survey observations, SPT-3G data is already providing tantalizing hints about what scientific goalposts will be possible in the very near future. I'll highlight a few of these results as well as providing perspectives on the upcoming CMB-S4 experiment.
Host: Albrecht Karle
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