The spectrum of a parametrized partial differential operator occurring in hydrodynamics

R. Denk, M. Möller, and C. Tretter

Abstract. An operator family of densely defined closed linear operators and the A partial differential operator associated with natural oscillations of an incompressible fluid in the neighbourhood of an elliptical flow is considered. The differentiation is only taken with respect to the angular variable, and thus the operator becomes a family of ordinary differential operators parametrized by the radial variable. It is shown that the spectra of these ordinary differential operators completely determine the spectrum of the given operator which turns out to have a kind of skeleton structure.

J. London Math. Soc. (2) 65 (2002), 483-492.

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