Liouville term for neutrinos: Flavor structure and wave interpretation

Mar 13, 2018
19 pages
Published in:
  • JCAP 05 (2018) 016
  • Published: May 4, 2018
e-Print:
Report number:
  • MPP-2018-14

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Abstract: (IOP)
Neutrino production, absorption, transport, and flavor evolution in astrophysical environments is described by a kinetic equation D=−i[H,]+[]. Its basic elements are generalized occupation numbers , matrices in flavor space, that depend on time t, space x, and momentum p. The commutator expression encodes flavor conversion in terms of a matrix H of oscillation frequencies, whereas [] represents source and sink terms as well as collisions. The Liouville operator on the left hand side involves linear derivatives in t, x and p. The simplified expression D=∂t+⋅∂x for ultra-relativistic neutrinos was recently questioned in that flavor-dependent velocities should appear instead of the unit vector . Moreover, a new damping term was postulated as a result. We here derive the full flavor-dependent velocity structure of the Liouville term although it appears to cause only higher-order corrections. Moreover, we argue that on the scale of the neutrino oscillation length, the kinetic equation can be seen as a first-order wave equation.
  • neutrino: oscillation
  • neutrino: production
  • operator: Liouville
  • correction: higher-order
  • oscillation: frequency
  • oscillation: length
  • derivative: linear
  • flavor
  • structure
  • velocity