Browsing by Author "Larsen, E. W."

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    Extension of Case formulas to Lp. Application to half and full space problems
    Larsen, E. W.; Sancaktar, Selim; Zweifel, Paul F. (AIP Publishing, 1975-05)
    The singular eigenfunction expansions originally applied by Case to solutions of the transport equation are extended from the space of Hölder‐continuous functions to the function spaces X p = {f‖μf (μ) ‐ L p }, where the expansions are now to be interpreted in the X p norm. The spectral family for the transport operator is then obtained explicitly, and is used to solve transport problems with X p sources and incident distributions.
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    On the spectrum of linear transport operator
    Larsen, E. W.; Zweifel, Paul F. (AIP Publishing, 1974-11)
    In this paper, spectral properties of the time_independent linear transport operator A are studied. This operator is defined in its natural Banach space L 1(D _ V), where D is the bounded space domain and V is the velocity domain. The collision operator K accounts for elastic and inelastic slowing down, fission, and low energy elastic and inelastic scattering. The various cross sections in K and the total cross section are piecewise continuous functions of position and speed. The two cases _0>0 and _0=0 are treated, where _0 is the minimum neutron speed. For _0=0, it is shown that _(A) consists of a full half_plane plus, in an adjoining strip, point eigenvalues and curves. For _0>0, _(A) consists just of point eigenvalues and curves in a certain half_space. In both cases, the curves are due to purely elastic ``Bragg'' scattering and are absent if this scattering does not occur. Finally the spectral differences between the two cases _0>0 and _0=0 are discussed briefly, and it is proved that A is the infinitesimal generator of a strongly continuous semigroup of operators.