It is shown that the order of Gateaux smoothness of bump functions on a wide class of Banach spaces with unconditional basis is not better than that of Fréchet differentiability. It is proved as well that in the separable case this order for Banach lattices satisfying a lower p-estimate for 1≤ p < 2 can be only slightly better.
Faculty of Mathematics and Informatics, Sofia University, 5, James Bourchier blvd, 1126 Sofia, Bulgaria
Departament d'Anàlisi Matemàtica, Universitat de València, Dr. Moliner, 50, 46100 Burjassot (València), Spain
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