POLYNOMIAL NUMERICAL INDEX FOR SOME COMPLEX VECTOR-VALUED FUNCTION SPACES

Abstract

We study in this paper the relation between the polynomial numerical indices of a complex vector-valued function space and the ones of its range space. It is proved that the spaces C(K,X), and L∞(μ,X) have the same polynomial numerical index as the complex Banach space X for every compact Hausdorff space K and every σ-finite measure μ, which does not hold any more in the real case. We give an example of a complex Banach space X such that, for every k > 2, the polynomial numerical index of order k of X is the greatest possible, namely 1, while the one of X∗∗ is the least possible, namely k k 1−k . We also give new examples of Banach spaces with the polynomial Daugavet property, namely L∞(μ,X) when μ is atomless, and Cw(K,X), Cw∗ (K,X ∗) when K is perfect.