Exact constants in direct and inverse approximation theorems for functions of several variables in the spaces S p
Fahreddin G Abdullayev, Pelin Özkartepe, Viktor V Savchuk, Andrii L Shidlich
In the paper, exact constants in direct and inverse approximation theorems for functions of several variables are found in the spaces S p. The equivalence between moduli of smoothness and some K-functionals is also shown in the spaces S p