Smooth, compact operators

Author:

Hennefeld Julien

Abstract

It is a result of Holub’s [Math. Ann. 201 (1973), 157-163], that for T a compact operator on a real Hilbert space, T is smooth T x 1 = T x 2 = T \Leftrightarrow \left \| {T{x_1}} \right \| = \left \| {T{x_2}} \right \| = \left \| T \right \| for some x 1 = x 2 = 1 \left \| {{x_1}} \right \| = \left \| {{x_2}} \right \| = 1 implies x 1 = ± x 2 {x_1} = \pm \;{x_2} . We extend this characterization of smooth, compact operators to a large class of Banach spaces, including l p , L p [ 0 , 1 ] {l_p},{L_p}[0,1] , and d ( a , p ) d(a,p) , with 1 > p > 1 > p > \infty . We show that for this same class of Banach spaces, one dimensional, norm one functionals in K ( X ) K{(X)^\ast } must be extremal. We also present examples of spaces for which Holub’s condition does not characterize smooth, compact operators.

Publisher

American Mathematical Society (AMS)

Subject

Applied Mathematics,General Mathematics

Reference5 articles.

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