Fast flavor instabilities and the search for neutrino angular crossings. (arXiv:2104.04106v1 [hep-ph])
<a href="http://arxiv.org/find/hep-ph/1/au:+Johns_L/0/1/0/all/0/1">Lucas Johns</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Nagakura_H/0/1/0/all/0/1">Hiroki Nagakura</a>
With the recognition that fast flavor instabilities likely affect supernova
and neutron-star-merger neutrinos, using simulation data to pin down when and
where the instabilities occur has become a high priority. The effort faces an
interesting problem. Fast instabilities are related to neutrino angular
crossings, but simulations often employ moment methods, sacrificing
momentum-space angular resolution in order to allocate resources elsewhere. How
can limited angular information be used most productively? The main aims here
are to sharpen this question and examine some of the available answers. A
recently proposed method of searching for angular crossings is scrutinized, the
limitations of moment closures are highlighted, and two ways of reconstructing
angular distributions solely from the flux factors (based respectively on
maximum-entropy and sharp-decoupling assumptions) are compared. In
(semi)transparent regions, the standard closure prescriptions likely miss some
crossings that should be there and introduce others that should not.
With the recognition that fast flavor instabilities likely affect supernova
and neutron-star-merger neutrinos, using simulation data to pin down when and
where the instabilities occur has become a high priority. The effort faces an
interesting problem. Fast instabilities are related to neutrino angular
crossings, but simulations often employ moment methods, sacrificing
momentum-space angular resolution in order to allocate resources elsewhere. How
can limited angular information be used most productively? The main aims here
are to sharpen this question and examine some of the available answers. A
recently proposed method of searching for angular crossings is scrutinized, the
limitations of moment closures are highlighted, and two ways of reconstructing
angular distributions solely from the flux factors (based respectively on
maximum-entropy and sharp-decoupling assumptions) are compared. In
(semi)transparent regions, the standard closure prescriptions likely miss some
crossings that should be there and introduce others that should not.
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