Abstract:
A new notion of weak monotonicity of sets is introduced, and it is shown that an approximatively compact and weakly monotone connected (weakly Menger-connected) set in a Banach space admits a continuous additive (multiplicative) $\varepsilon $-selection for any $\varepsilon >0$. Then a notion of weak monotone connectedness (weak Menger connectedness) of sets with respect to a set of $d$-defining functionals is introduced. For such sets, continuous $(d^{-1},\varepsilon )$-selections are constructed on arbitrary compact sets.
Citation:
I. G. Tsar'kov, “Weakly monotone sets and continuous selection from a near-best approximation operator”, Harmonic analysis, approximation theory, and number theory, Collected papers. Dedicated to Academician Sergei Vladimirovich Konyagin on the occasion of his 60th birthday, Trudy Mat. Inst. Steklova, 303, MAIK Nauka/Interperiodica, Moscow, 2018, 246–257; Proc. Steklov Inst. Math., 303 (2018), 227–238