Cosmo-Astro Seminar | Fundamental Physics with kSZ Tomography: Progress and Challenges

As CMB photons traverse through the late universe, they scatter with electrons caught up in bulk flows of large-scale structure, a phenomenon known as the kinetic Sunyaev Zel'dovich (kSZ) effect. By cross-correlating CMB maps with galaxy surveys, the kSZ effect therefore allows us to tomographically reconstruct the velocity field of large-scale structure, which contains a wealth of cosmological information. In the last decade, this emerging program of kSZ tomography for cosmological inference has shown great progress, with many new theoretical applications and continual improvements in data analysis. However, very recently, kSZ velocity reconstructions with ACT and DESI data have shown a small signal than predicted by theoretical models. This discrepancy may point us to new physical insights, for example about baryonic feedback, and ultimately raises questions about the future prospects of constraining cosmology with kSZ tomography. In this talk, I will discuss the recent rapid development in kSZ tomography, highlight the challenge that these new measurements present to us, and suggest a path forward.