RUI: Quantum Kinetics of Neutrinos: Studying the Universe at the Interface of Neutrino and Nuclear Astrophysics

Every second, trillions of neutrinos pass through our bodies, leaving nary a trace. On the other hand, in the first few minutes of the lifetime of the universe — a mere blink of the eye in the 13.8 billion year history of the universe from the Big Bang to the present day — the universe is so hot and so dense that neutrinos, in spite of the weakness of their interactions with matter, play an important role in the dynamics of this early epoch in the history of the universe.

As a result, the early universe provides an interesting environment to study fundamental physics that may be either difficult or impossible to probe in the terrestrial laboratory. This project looks to leverage upcoming advances in upcoming high-precision cosmological observations to use the dynamics of the early universe to explore fundamental physics.

The PI will train undergraduate student researchers, and as they engage in this intriguing field of study, they will build various skills that are valuable across a range of 21st century careers. In performing this work, they will numerically simulate neutrino evolution in astrophysical environments along with the concomitant effect on their environment.

These simulations will explore the complex evolution of neutrinos that are influenced by their quantum mechanical nature and by many interactions with other neutrinos and their environment.

This project will explore the quantum kinetic evolution of neutrinos in the early universe where this evolution is driven by the hot and dense environment as well as large fluxes of neutrinos. The quantum kinetic neutrino evolution is affected by their coherent, unitary quantum mechanical behavior, their high scattering rates, and nonlinearity introduced by neutrino-neutrino interactions.

In the early universe — the first few minutes after the Big Bang — this nonlinear quantum kinetic behavior plays an important role in the dynamics of the universe as well as the interconversion between protons and neutrons. A self-consistent exploration of this behavior is needed too understand its effects on cosmological observables as well as the synthesis of elements in Big Bang Nucleosynthesis.

The goal of this project is to solve the quantum kinetic equations in the early universe to build a broader understanding of the nonlinear quantum kinetic evolution of neutrino states in this environment, to elucidate the feedback of this evolution, and toward the goal of leveraging upcoming anticipated high-precision cosmological observations complemented by high-fidelity theoretical calculations to treat the universe as a laboratory to study fundamental physics.

This project advances the objectives of "Windows on the Universe: the Era of Multi-Messenger Astrophysics", one of the 10 Big Ideas for Future NSF Investments.

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.