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Spectraloid operator polynomials, the approximate numerical range and an Eneström-Kakeya theorem in Hilbert space

100%

Swoboda J., Wimmer H.

Studia Mathematica

2010

tom 198

nr 3

279-300

We study a class of operator polynomials in Hilbert space which are spectraloid in the sense that spectral radius and numerical radius coincide. The focus is on the spectrum in the boundary of the numerical range. As an application, the Eneström-Kakeya-Hurwitz theorem on zeros of real polynomials is generalized to Hilbert space.

Estimates for projections in Banach spaces and existence of direct complements

81%

Dirr G., Rakočević V., Wimmer H.

Studia Mathematica

2005

tom 170

nr 2

211-216

Let W and L be complementary subspaces of a Banach space X and let P(W,L) denote the projection on W along L. We obtain a sufficient condition for a subspace M of X to be complementary to W and we derive estimates for the norm of P(W,L) - P(W,M).

Ograniczanie wyników

2 Studia Mathematica

2 Wimmer H.

1 Dirr G.

1 Rakočević V.

1 Swoboda J.

1 2010

1 2005

Wyniki wyszukiwania

Spectraloid operator polynomials, the approximate numerical range and an Eneström-Kakeya theorem in Hilbert space

Estimates for projections in Banach spaces and existence of direct complements