The successful transition from core-collapse supernova simulations using
classical neutrino transport to simulations using quantum neutrino transport
will require the development of methods for calculating neutrino flavor
transformations that mitigate the computational expense. One potential approach
is the use of angular moments of the neutrino field, which has the added appeal
that there already exist simulation codes which make use of moments for
classical neutrino transport. Evolution equations for quantum moments based on
the quantum kinetic equations can be straightforwardly generalized from the
evolution of classical moments based on the Boltzmann equation. We present an
efficient implementation of neutrino transformation using quantum angular
moments in the free streaming, spherically symmetric bulb model. We compare the
results against analytic solutions and the results from more exact multi-angle
neutrino flavor evolution calculations. We find that our moment-based methods
employing scalar closures predict, with good accuracy, the onset of collective
flavor transformations seen in the multi-angle results. However in some
situations they overestimate the coherence of neutrinos traveling along
different trajectories. More sophisticated quantum closures may improve the
agreement between the inexpensive moment-based methods and the multi-angle
approach.Comment: Accepted in Physical Review