RUI: Quantum Kinetics of Neutrinos: a window on nuclear and particle astrophysics in the Early Universe and Compact Objects

University Of San Diego, San Diego CA

Investigators

Abstract

Neutrinos are particles that travel through the universe at the speed of light, but very rarely interact with matter. Trillions of neutrinos pass through our bodies every second without leaving a trace. In hot and dense astrophysical environments, prodigious numbers of neutrinos significantly impact each other and their environment. Here, neutrinos play an important role in energy transport, affecting the dynamics of these environments, and in converting protons to neutrons and vice-versa, affecting the synthesis of elements. Therefore, understanding how neutrinos evolve is essential to addressing intriguing topics in astrophysics, including understanding the origins of the elements and using precise observations to elucidate fundamental physics. The PI will train undergraduate researchers, engaging them in various skills that are valuable across a range of 21st century careers. They will simulate numerically the evolution of neutrinos in astrophysical environments and their concomitant effect on their environment. This evolution is complicated by the quantum mechanical nature of particles, interactions of neutrinos with other neutrinos, and the high rate at which they collide. In addition to mentoring undergraduate researchers, the PI will broaden the impact of this project by enhancing outreach projects run by the Society of Physics Students chapter at the University of San Diego. This project will study the evolution of neutrinos in hot and dense astrophysical environments where prodigious fluxes of neutrinos affect the dynamics of their environment. Here, neutrino evolution is complicated by their nonlinear evolution due to neutrino-neutrino interactions, their coherent, quantum mechanical behavior, and their high scattering rates (kinetics) that influence the aforementioned effects. In environments such as the early universe, within the first second after the Big Bang, and the explosive end of stars' lives, this nonlinear quantum kinetic behavior plays an important role because neutrinos transport energy over large length scales and govern the interconversion between protons and neutrons. These effects need to be self-consistently understood in order to better understand the synthesis of the elements and to perform the high-precision calculations needed to complement high-precision cosmological observations that look to use the universe as a laboratory to study fundamental physics. The quantum kinetic equations for neutrino evolution in astrophysical environments are known. The goal of this project is to solve these equations in astrophysical environments toward toward gaining a broader understanding of the nonlinear quantum kinetic evolution of neutrino states and to elucidate the feedback of this evolution on the astrophysical environments. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.