Riesz summation method

From Encyclopedia of Mathematics
Jump to: navigation, search

A method for summing series of numbers and functions; denoted by $(R,\lambda,k)$. A series $\sum_{n=0}^\infty a_n$ is summable by the Riesz summation method $(R,\lambda,k)$ to the sum $s$ if


where $k>0$, $0\leq\lambda_0<\dotsb<\lambda_n\to\infty$, and $\omega$ is a continuous parameter. The method was introduced by M. Riesz [1] for the summation of Dirichlet series. The method $(R,\lambda,k)$ is regular; when $\lambda_n=n$ it is equivalent to the Cesàro summation method $(C,k)$ (cf. Cesàro summation methods), and these methods are compatible (cf. Compatibility of summation methods).

Riesz considered also a method in which summability of the series $\sum_{n=0}^\infty a_n$ is defined by means of the limit of the sequence $\{\sigma_m\}$, where


$$P_m=\sum_{k=0}^mp_k\neq0,\quad s_k=\sum_{n=0}^ka_n.$$

This method is denoted by $(R,p_n)$. The method $(R,\lambda,k)$ is a modification of the method $(R,p_n)$ (when $k=1$) and is a generalization of it to the case of an arbitrary $k>0$.


[1] M. Riesz, "Une méthode de sommation équivalente à la méthode des moyennes arithmétique" C.R. Acad. Sci. Paris , 152 (1911) pp. 1651–1654
[2] F. Riesz, "Sur la sommation des séries de Dirichlet" C.R. Acad. Sci. Paris , 149 (1909) pp. 18–21
[3] G.H. Hardy, M. Riesz, "The general theory of Dirichlet series" , Cambridge Univ. Press (1915)
[4] G.H. Hardy, "Divergent series" , Clarendon Press (1949)



[a1] K. Zeller, W. Beekmann, "Theorie der Limitierungsverfahren" , Springer (1970)
How to Cite This Entry:
Riesz summation method. Encyclopedia of Mathematics. URL:
This article was adapted from an original article by I.I. Volkov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article