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Constraining Inflation with Cosmic Microwave Background Polarization Measurements
Speaker Dr. Kimmy Wai Ling Wu, University of Chicago
Date 12 March 2018 (Monday)
Time 10:30 - 12:00
Venue Room 4621 (Lifts 31-32), HKUST

Inflation describes the near-exponential expansion of the universe in the first fractions of a second. It generically predicts a background of primordial gravitational waves, which generate a primordial B-mode component in the polarization of the cosmic microwave background (CMB). The measurement of such a B-mode signature would lend significant support to the paradigm of inflation and be important for development of quantum gravity theories. However, any measured B-modes will also contain a component from the gravitational lensing of primordial E modes, which can obscure the measurement of the primordial B modes. If the amplitude of primordial B modes is sufficiently small, the lensing component will need to be cleaned using a process called ‘delensing.’ Delensing has been studied theoretically and with simulations but has not been demonstrated with data until recently. I will present delensing of a measurement of the CMB B-mode power spectrum from SPTpol using data from Herschel as a tracer of the lensing potential. The measured B-mode power is reduced by 28 percent on sub-degree scales, in agreement with predictions from simulations, and the null hypothesis of no delensing is ruled out at 6.9 sigma (arXiv: 1701.04396). Then I will give an update on the current delensing effort on the BICEP/Keck data. This analysis will reduce the uncertainty in the constraint in the primordial B modes (parameterized through the tensor-to-scalar ratio, r ). Finally, I will conclude with an outlook of constraining inflation with upcoming and future experiments.


Kimmy Wu is a KICP Fellow at the University of Chicago Kavli Institute of Cosmological Physics. She is an experimental cosmologist specializing on the Cosmic Microwave Background radiation (CMB). She received a B.S. degree in Mathematics and Physics from the University of Michigan, Ann Arbor and a Ph.D in Physics from Stanford University. Her research is focused on searching for new physics through precision measurements of the cosmic microwave background. In particular, She is interested in using the polarization of CMB radiation to look for imprints of the stochastic background of gravitational waves from inflation. She works on many aspects of the program; forecast of science reach of future experiments, the designing and building of telescopes, and interpretation of data. She is currently members of the BICEP/Keck and South Pole Telescope collaborations.