Quantum Closures for Neutrino Moment Transport

• Main Authors: Kneller, James P, Froustey, Julien, Grohs, Evan B, Foucart, Francois, McLaughlin, Gail C, Richers, Sherwood
• Format: Journal Article
• Language: English
• Published: 01.10.2024
• Subjects: Physics - High Energy Astrophysical Phenomena; Physics - High Energy Physics - Phenomenology; Physics - Nuclear Theory
• DOI: 10.48550/arxiv.2410.00719

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. This parameterization paves the way to setting prescriptions for genuine quantum closures adapted to neutrino transport in a range of situations.