A generalized -porous set with a small complement.
A hierarchy in the family of real surjective functions
This expository paper focuses on the study of extreme surjective functions in ℝℝ. We present several different types of extreme surjectivity by providing examples and crucial properties. These examples help us to establish a hierarchy within the different classes of surjectivity we deal with. The classes presented here are: everywhere surjective functions, strongly everywhere surjective functions, κ-everywhere surjective functions, perfectly everywhere surjective functions and Jones functions. The...
A note on iteration groups.
A note on partial derivatives of convex functions
A roller coaster approach to integration and Peano's existence theorem
This is a didactic proposal on how to introduce the Newton integral in just three or four sessions in elementary courses. Our motivation for this paper were Talvila's work on the continuous primitive integral and Koliha's general approach to the Newton integral. We introduce it independently of any other integration theory, so some basic results require somewhat nonstandard proofs. As an instance, showing that continuous functions on compact intervals are Newton integrable (or, equivalently, that...
An almost nowhere Fréchet smooth norm on superreflexive spaces
Every separable infinite-dimensional superreflexive Banach space admits an equivalent norm which is Fréchet differentiable only on an Aronszajn null set.
An analysis of the Rüschendorf transform - with a view towards Sklar’s Theorem
We revisit Sklar’s Theorem and give another proof, primarily based on the use of right quantile functions. To this end we slightly generalise the distributional transform approach of Rüschendorf and facilitate some new results including a rigorous characterisation of an almost surely existing “left-invertibility” of distribution functions.
An example of a continuous function without the usual, the approximative and the distributional derivative
An infinite-dimensional subspace of consisting of functions with no finite one-sided derivatives.
An o-minimal structure which does not admit cellular decomposition
We present an example of an o-minimal structure which does not admit cellular decomposition. To this end, we construct a function whose germ at the origin admits a representative for each integer , but no representative. A number theoretic condition on the coefficients of the Taylor series of then insures the quasianalyticity of some differential algebras induced by . The o-minimality of the structure generated by is deduced from this quasianalyticity property.
Analyse 2-microlocale et développementen série de chirps d'une fonction de Riemann et de ses généralisations
En dimension 1 on analyse la fonction irrégulière (p entier ≥ 2) en un point de dérivabilité (π est un tel point) et on démontre que le terme d’erreur est un chirp de classe (1 + 1/(2p-2), 1/(p-1), (p-1)/p). La fonction r(x) est dans l’espace 2-microlocal si et seulement si s+s’ ≤ 1 - 1/p et ps+s’≤ p - 1/2. En dimension 2, on obtient en (π,π) l’existence d’un plan tangent pour la surface dès que γ>1.
Approximate differentiation: Jarník points
Approximate smoothness of continuous functions
Characterization of compact subsets of curves with ω-continuous derivatives
We give a characterization of compact subsets of finite unions of disjoint finite-length curves in ℝⁿ with ω-continuous derivative and without self-intersections. Intuitively, our condition can be formulated as follows: there exists a finite set of regular curves covering a compact set K iff every triple of points of K behaves like a triple of points of a regular curve. This work was inspired by theorems by Jones, Okikiolu, Schul and others that characterize compact subsets of...
Charakterisierungen von nirgends differenzierbaren Weierstraß-Funktionen durch Replikativität.
Comportement local moyen de la fonction de Brjuno
We describe the average behaviour of the Brjuno function Φ in the neighbourhood of any given point of the unit interval. In particular, we show that the Lebesgue set of Φ is the set of Brjuno numbers and we find the asymptotic behaviour of the modulus of continuity of the integral of Φ.
Decompositions of compact convex sets.
Derivácia a spojitosť
Devil's staircases, ramps, humps and roller coasters
Differential estimate for -ary forms on closed orthants.