Summary
We establish functional equations for peculiar functionsf:I → ℝ,I ⊂ ℝ an interval, such as
- (1)
continuous, nowhere differentiable functions of various types (Weierstrass, Takagi, Knopp, Wunderlich),
- (2)
Riemann's function, which is nondifferentiable except on certain rational points,
- (3)
singular functions of various types (Cantor, Minkowski, de Rham).
All these functional equations take the form where thehv are given rational functions,g is a given function andα is a given real constant. For each of the above mentioned peculiar functions we discuss the essential non-differentiability properties and present at least one characterization by means of functional equations of type (F). Solutionsf:I → ℝ of the system of replicativity equations (all of type (F)) exhibit a particularly rich structure and are discussed in some detail.
$$+\sum\limits_{v = 1}^n {f[h_v (x)] = \alpha f(x) + g(x),} x \in I,$$
(F)
$$\frac{1}{p}\sum\limits_{k = 0}^{p - 1} {f\left( {\frac{{x + k}}{p}} \right) = (p)f(x), p \in S \subset \mathbb{N}} $$
AMS (1991) subject classification
Primary 39B22, 39B62 Secondary 26A27, 26A30Preview
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