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For a real analytic periodic function $phi:mathbb{R}to mathbb{R}$, an integer $bge 2$ and $lambdain (1/b,1)$, we prove the following dichotomy for the Weierstrass-type function $W(x)=sumlimits_{nge 0}{{lambda}^nphi(b^nx)}$: Either $W(x)$ is real analytic, or the Hausdorff dimension of its graph is equal to $2+log_blambda$. Furthermore, given $b$ and $phi$, the former alternative only happens for finitely many $lambda$ unless $phi$ is constant.
Let $f$ be a $C^{2+epsilon}$ expanding map of the circle and $v$ be a $C^{1+epsilon}$ real function of the circle. Consider the twisted cohomological equation $v(x) = alpha (f(x)) - Df(x) alpha (x)$ which has a unique bounded solution $alpha$. We pro
We show that the graph of the classical Weierstrass function $sum_{n=0}^infty lambda^n cos (2pi b^n x)$ has Hausdorff dimension $2+loglambda/log b$, for every integer $bge 2$ and every $lambdain (1/b,1)$. Replacing $cos(2pi x)$ by a general non-const
We investigate Weierstrass functions with roughness parameter $gamma$ that are Holder continuous with coefficient $H={loggamma}/{log frac12}.$ Analytical access is provided by an embedding into a dynamical system related to the baker transform where
For nonautonomous linear difference equations, we introduce the notion of the so-called nonuniform dichotomy spectrum and prove a spectral theorem. Moreover, we introduce the notion of weak kinematical similarity and prove a reducibility result by the spectral theorem.
In this paper we study several stronger forms of sensitivity for continuous surjective selfmaps on compact metric spaces and relations between them. The main result of the paper states that a minimal system is either multi-sensitive or an almost one-