Special Physics Seminar

CMB Lensing: Fundamental Physics from Maps of the Invisible

Blake Sherwin

Lawrence Berkeley National Laboratory

Dark matter not only forms an invisible cosmic scaffolding within which galaxies form, its distribution in the universe also contains a wealth of information about neutrinos, dark energy, and physics at the earliest times. Measurements of gravitational lensing in the cosmic microwave background (CMB) allow this matter distribution to be directly seen and mapped. In my talk, I will first discuss recent measurements of CMB lensing and what they imply for physics. I will then explain why future measurements of the CMB lensing signal, with experiments such as Simons Observatory, will be remarkably powerful probes of neutrinos and dark energy. Lensing is not only a signal, however, but also a source of noise that limits how much we can learn about the very early universe. With illustrations from recent work, I will explain why delensing - removing the lensing effect to reveal the primordial sky - is crucial for the future of CMB cosmology.