We give an example of a positive operator B in a Krein space with the following properties: the nonzero spectrum of B consists of isolated simple eigenvalues, the norms of the orthogonal spectral projections in the Krein space onto the eigenspaces of B are uniformly bounded and the point ∞ is a singular critical point of B.
Proceedings of the American Mathematical Society
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First published in "Proceedings of the American Mathematical Society" in 2000, published by the American Mathematical Society.
Ćurgus, Branko; Gheondea, Aurelian; and Langer, Heinz, "On Singular Critical Points of Positive Operators in Krein Spaces" (2000). Mathematics. Paper 8.