As the cosmic microwave background (CMB) photons stream to us from the early universe, they pass by the inhomogeneous distribution of dark matter in the universe and get gravitationally deflected. This leads to a distorted view of the primordial fluctuations in the CMB at our end. These subtle distortions contain information about how structure has evolved across different scales and can be used as a sensitive probe of the total mass in neutrinos and the nature of dark energy. This signal has recently been detected directly in the CMB using observations from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) and can also be used to test general relativity on cosmological scales. Soon, high resolution polarization experiments, such as PolarBear, ACTPol, and SPTPol will be in full swing, letting us measure this signal with high precision. In this talk, I will explain this effect, describe its first detection, and discuss the potential of the future measurements as a probe of cosmology and particle physics.

Argonne Physics Division Colloquium Schedule