Physics Colloquium with Adrian Bayer

Abstract: Neutrinos are the only known particles whose absolute mass scale remains undetermined, and measuring it precisely is a key target for both particle physics and cosmology, providing a window into physics beyond the Standard Model. In this talk, I will focus on neutrino mass as a case study for how cosmological data can probe fundamental physics, and why the coming era of high-resolution, high-volume surveys demands new simulations and inference methods.

Due to their low masses and high thermal velocities, neutrinos free-stream over large distances, suppressing the growth of cosmic structure in a distinctive way. I will first show how different components of the cosmic web can be leveraged to break parameter degeneracies and extract significantly more information about neutrino mass than traditional cosmological methods. Building on this, I will present field-level inference as an optimal approach for extracting information from cosmic structure, showcasing how it can improve measurements from galaxy surveys by reconstructing the initial conditions of the Universe. Beyond galaxy surveys, the next generation of cosmological discovery will be defined by combining information from multiple cosmological datasets—including weak lensing and the cosmic microwave background—to tighten constraints, mitigate systematics, and detect otherwise undetectable signals. I will end by highlighting work from the Simons Observatory’s Sky Modeling group to enable such joint analyses and accelerate fundamental physics discovery over the coming decade.