Quantum Closures for Neutrino Moment Transport

Understand

A computationally efficient method for calculating the transport of neutrino flavor in simulations is to use angular moments of the neutrino one-body reduced density matrix, i.e., `quantum moments'.

• As with any moment-based radiation transport method, a closure is needed if the infinite tower of moment evolution equations is truncated.
• We derive a general parameterization of a quantum closure and the limits the parameters must satisfy in order for the closure to be physical.
• We then derive from multi-angle calculations the evolution of the closure parameters in two test cases which we then progressively insert into a moment evolution code and show how the parameters affect the moment results until the full multi-angle results are reproduced.