CMB Lensing: Fundamental Physics from Maps of the Invisible
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, inflation, and dark energy. Measurements of gravitational lensing in the cosmic microwave background (CMB) allow this matter distribution to be directly seen and mapped out to high redshifts. In my talk, I will discuss current and future work in this new but rapidly advancing field. In particular, I will show new measurements of CMB lensing with the ACTPol experiment and discuss the promise of future ultra-high-precision studies of the lensing signal with the Simons Observatory and CMB Stage-IV experiments. Lensing is not only a signal, however, but also a source of noise that limits how much we can learn about the early universe via B-mode polarization. In my talk, I will explain why delensing - removing the lensing effect to reveal the primordial sky - is crucial for the future of CMB science, showing recent work in this new area.