Note on a Theorem of Kuratowski-Sierpiński
Given a modulus of continuity and then denotes the space of all functions with the period on that are locally integrable in power and whose integral modulus of continuity of power (see(1)) is majorized by a multiple of . The moduli of continuity are characterized for which contains “many” functions with infinite “essential” variation on an interval of length .
We solve Matkowski's problem for strictly comparable quasi-arithmetic means.
We investigate functions f: I → ℝ (where I is an open interval) such that for all u,v ∈ I with u < v and f(u) ≠ f(v) and each c ∈ (min(f(u),f(v)),max(f(u),f(v))) there is a point w ∈ (u,v) such that f(w) = c and f is approximately continuous at w.
The concept of almost quasicontinuity is investgated in this paper in several directions (e.g. the relation of this concept to other generalizations of continuity is described, various types of convergence of sequences of almost quasicontinuous function are studied, a.s.o.).