On the best approximations and rate of convergence of decompositions in the root vectors of an operator

• Дата: 1997
• Автори: Radzievskii, G. V., Радзиевский, Г. В.
• Формат: Стаття
• Мова: Російська; Англійська
• Опубліковано: Institute of Mathematics, NAS of Ukraine 1997
• Онлайн доступ: https://umj.imath.kiev.ua/index.php/umj/article/view/5060
• Назва журналу: Ukrains’kyi Matematychnyi Zhurnal

We establish upper bounds of the best approximations of elements of a Banach space B by the root vectors of an operator $A$ that acts in B. The corresponding estimates of the best approximations are expressed in terms of a K-functional associated with the operator A. For the operator of differentiat...