MathDB
Miklos Schweitzer 1951_2

Source:

October 8, 2008
functionalgebrapolynomialreal analysisreal analysis unsolved

Problem Statement

Denote by H \mathcal{H} a set of sequences S\equal{}\{s_n\}_{n\equal{}1}^{\infty} of real numbers having the following properties: (i) If S\equal{}\{s_n\}_{n\equal{}1}^{\infty}\in \mathcal{H}, then S'\equal{}\{s_n\}_{n\equal{}2}^{\infty}\in \mathcal{H}; (ii) If S\equal{}\{s_n\}_{n\equal{}1}^{\infty}\in \mathcal{H} and T\equal{}\{t_n\}_{n\equal{}1}^{\infty}, then S\plus{}T\equal{}\{s_n\plus{}t_n\}_{n\equal{}1}^{\infty}\in \mathcal{H} and ST\equal{}\{s_nt_n\}_{n\equal{}1}^{\infty}\in \mathcal{H}; (iii) \{\minus{}1,\minus{}1,\dots,\minus{}1,\dots\}\in \mathcal{H}. A real valued function f(S) f(S) defined on H \mathcal{H} is called a quasi-limit of S S if it has the following properties: If S\equal{}{c,c,\dots,c,\dots}, then f(S)\equal{}c; If si0 s_i\geq 0, then f(S)0 f(S)\geq 0; f(S\plus{}T)\equal{}f(S)\plus{}f(T); f(ST)\equal{}f(S)f(T), f(S')\equal{}f(S) Prove that for every S S, the quasi-limit f(S) f(S) is an accumulation point of S S.