Smoothness of functions and Fourier coefficients
    
    
  
  
  
      
      
      
        
Sbornik. Mathematics, Tome 210 (2019) no. 7, pp. 994-1018
    
  
  
  
  
  
    
      
      
        
      
      
      
    Voir la notice de l'article provenant de la source Math-Net.Ru
            
              			We consider functions represented as trigonometric series with general monotone Fourier coefficients. The main result of the paper is the equivalence of the $L_p$ modulus of smoothness, $1$, of such functions to certain sums of their Fourier coefficients. As applications, for such functions we give a description of the norm in the Besov space and sharp direct and inverse theorems in approximation theory.
Bibliography: 34 titles.
			
            
            
            
          
        
      
                  
                    
                    
                    
                        
Keywords: 
Fourier series, general monotone sequences, moduli of smoothness.
                    
                    
                    
                  
                
                
                @article{SM_2019_210_7_a2,
     author = {M. I. Dyachenko and A. B. Mukanov and S. Yu. Tikhonov},
     title = {Smoothness of functions and {Fourier} coefficients},
     journal = {Sbornik. Mathematics},
     pages = {994--1018},
     publisher = {mathdoc},
     volume = {210},
     number = {7},
     year = {2019},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_2019_210_7_a2/}
}
                      
                      
                    M. I. Dyachenko; A. B. Mukanov; S. Yu. Tikhonov. Smoothness of functions and Fourier coefficients. Sbornik. Mathematics, Tome 210 (2019) no. 7, pp. 994-1018. http://geodesic.mathdoc.fr/item/SM_2019_210_7_a2/
