Extreme Contractions on Finite-Dimensional Polygonal Banach Spaces

D. Sain ; A. Ray ; K. Paul

Journal of convex analysis, Tome 26 (2019) no. 3, pp. 877-885

Résumé

We explore extreme contractions on finite-dimensional polygonal Banach spaces, from the point of view of attainment of norm of a linear operator. We prove that if $X$ is an $n$-dimensional polygonal Banach space and $Y$ is any normed linear space and $T \in L(X,Y)$ is an extreme contraction, then $T$ attains norm at $n$ linearly independent extreme points of $B_{X}$. Moreover, if $T$ attains norm at $n$ linearly independent extreme points $x_1, x_2, \ldots, x_n$ of $B_X$ and does not attain norm at any other extreme point of $B_X$, then each $Tx_i$ is an extreme point of $ B_Y.$ We completely characterize extreme contractions between a finite-dimensional polygonal Banach space and a strictly convex normed linear space. We introduce L-P property for a pair of Banach spaces and show that it has natural connections with our present study. We also prove that for any strictly convex Banach space $X$ and any finite-dimensional polygonal Banach space $Y$, the pair $(X,Y)$ does not have L-P property. Finally, we obtain a characterization of Hilbert spaces among strictly convex Banach spaces in terms of L-P property.

Détail

Classification : 46B20, 47L05
Mots-clés : Extreme contractions, polygonal Banach spaces, strict convexity, Hilbert spaces