PHYS/ASTR Colloquium: "Testing Inflation and Constraining Cosmology with the Oldest Photons" - Dr. Kimmy Wu (Postdoc, Stanford)

San Francisco State University

Physics & Astronomy Colloquium Series

Monday, February 19, 2024

Thornton Hall 411, 3:30 PM

"Testing Inflation and Constraining Cosmology with the Oldest Photons"

Dr. Kimmy Wu (Postdoc, Stanford U./SLAC)

Inflation -- the leading model for the earliest moments of the time, in which the Universe undergoes a period of rapid, accelerating expansion -- generically predicts a background of primordial gravitational waves, which generate a 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. However, observed B modes also contain a component from the gravitational lensing of primordial E modes, which can obscure the measurement of the primordial B modes. We reduce the uncertainties in the B-mode measurement contributed from this lensing component by a technique called 'delensing.’ In this talk, I will show results of the first and only analysis that reduces cosmological parameter uncertainty, in this case the uncertainty on the tensor-to-scalar ratio from the BICEP/Keck experiments, with delensing.

For upcoming analyses, efficient delensing relies on high signal-to-noise measurements of the CMB lensing mass map. Such lensing maps not only will be essential for testing inflation, they will also provide new cosmological information compared to the primary CMB. This is particularly interesting in light of the current tensions between inferred parameter values of the standard cosmological model LCDM such as the Hubble parameter using different data sets. I will show the latest state-of-the-art measurement of CMB lensing using data from the South Pole Telescope, its cosmological parameter constraints, and discuss implications for cosmic tensions and the sum of neutrino masses.