where | (2.11) |

This is known as the ``1+2''-Boltzmann equation. Note that also the input data has to fulfill this symmetry. Consequently the cylinder radial components of the electrical field vanish.

With this assumption we have

(2.12) |

and

(2.13) |

Hence the BTE reduces for parabolic bands to

(2.14) |

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R. Kosik: Numerical Challenges on the Road to NanoTCAD