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We will prove that there exists a model of ZFC+``c= omega_2'' in which every M subseteq R of cardinality less than continuum c is meager, and such that for every X subseteq R of cardinality c there exists a continuous function f:R-> R with…

Logic · Mathematics 2016-09-07 Krzysztof Ciesielski , Saharon Shelah

We show that $ZF+DC+$"all Turing invariant sets of reals have the perfect set property" implies that all sets of reals have the perfect set property. We also show that this result generalizes to all countable analytic equivalence relations.

Logic · Mathematics 2020-04-06 Clovis Hamel , Haim Horowitz , Saharon Shelah

We show that in contrast with the Cohen version of Solovay's model, it is consistent for the continuum to be Cohen-measurable and for every function to be continuous on a non-meagre set.

Logic · Mathematics 2013-09-17 Noam Greenberg , Saharon Shelah

We give a new proof of a classical theorem on approximation of continuous functions on totally real sets

Complex Variables · Mathematics 2008-05-23 Bo Berndtsson

It is shown that it is consistent with ZFC that every uncountable set can be continuously mapped onto a splitting family.

Logic · Mathematics 2007-05-23 Tomek Bartoszynski

We investigate the asymptotic densities of theorems provable in Zermelo-Fraenkel set theory ZF and its extension ZFC including the axiom of choice. Assuming a canonical De Bruijn representation of formulae, we construct asymptotically large…

Logic · Mathematics 2021-01-26 Maciej Bendkowski

We show the consistency of ZFC +''there is no NWD-ultrafilter on omega'', which means: for every non principle ultrafilter D on the set of natural numbers, there is a function f from the set of natural numbers to the reals, such that for…

Logic · Mathematics 2009-09-25 Saharon Shelah

We prove that it is consistent with ZFC that for every non-decreasing function $f:[0,1]\to [0,1]$, each subset of $[0,1]$ of cardinality $\mathfrak c$ contains a set of cardinality $\mathfrak c$ on which $f$ is uniformly continuous. We show…

Logic · Mathematics 2025-03-03 Roman Pol , Piotr Zakrzewski , Lyubomyr Zdomskyy

We investigate which infinite binary sequences (reals) are effectively random with respect to some continuous (i.e., non-atomic) probability measure. We prove that for every n, all but countably many reals are n-random for such a measure,…

Logic · Mathematics 2021-04-06 Jan Reimann , Theodore A. Slaman

We give a short proof, that can be used in an introductory real analysis course, that if a function that is defined on the set of real numbers is continuous on a countable dense set, then it is continuous on an uncountable set. This is done…

Classical Analysis and ODEs · Mathematics 2023-03-27 Cesar E. Silva , Yuxin Wu

We prove it consistent relative to ZFC that all nontrivial forcings of size $\aleph _1$ add a Cohen real.

Logic · Mathematics 2009-09-25 Jindřich Zapletal

We show that it is consistent relative to ZF, that there is no well-ordering of $\mathbb{R}$ while a wide class of special sets of reals such as Hamel bases, transcendence bases, Vitali sets or Bernstein sets exists. To be more precise, we…

Logic · Mathematics 2022-08-02 Jonathan Schilhan

Let $f\colon\mathbb{R}^2\to\mathbb{R}$. The notions of feebly continuity and very feebly continuity of $f$ at a point $\langle x,y\rangle\in\mathbb{R}^2$ were considered by I. Leader in 2009. We study properties of the sets $FC(f)$…

General Topology · Mathematics 2019-10-29 Marek Balcerzak , Tomasz Natkaniec , Małgorzata Terepeta

We show in ZFC that there is no set of reals of size continuum which can be translated away from every set in the Marczewski ideal. We also show that in the Cohen model, every set with this property is countable.

Logic · Mathematics 2024-01-10 Joerg Brendle , Wolfgang Wohofsky

We are interested in subgroups of the reals that are small in one and large in another sense. We prove that, in ZFC, there exists a non-meager Lebesgue null subgrooup of R, while it isconsistent there there is no non-null meager subgroup of…

Logic · Mathematics 2016-06-01 Andrzej Roslanowski , Saharon Shelah

Using forcing with measured creatures we build a universe of set theory in which: (a) every sup-measurable function f:RxR-->R is measurable, and (b) every function f:R-->R is continuous on a non-measurable set. This answers a question of…

Logic · Mathematics 2013-01-03 Andrzej Roslanowski , Saharon Shelah

We show that (1) If ZF is consistent then the following theory is consistent "ZF + DC(omega_{1}) + Every set of reals has Baire property" and (2) If ZF is consistent then the following theory is consistent "ZFC + `every projective set of…

Logic · Mathematics 2019-08-27 Haim Judah , Saharon Shelah

Let f be a real entire function whose set S(f) of singular values is real and bounded. We show that, if f satisfies a certain function-theoretic condition (the "sector condition"), then $f$ has no wandering domains. Our result includes all…

Dynamical Systems · Mathematics 2014-12-10 Helena Mihaljević-Brandt , Lasse Rempe-Gillen

Absolute continuity implies uniform continuity, but generally not vice versa. In this short note, we present one sufficient condition for a uniformly continuous function to be absolutely continuous, which is the following theorem: For a…

Classical Analysis and ODEs · Mathematics 2015-03-17 Kai Yang , Chenhong Zhu

We show that the theory ZFC-, consisting of the usual axioms of ZFC but with the power set axiom removed-specifically axiomatized by extensionality, foundation, pairing, union, infinity, separation, replacement and the assertion that every…

Logic · Mathematics 2015-08-05 Victoria Gitman , Joel David Hamkins , Thomas A. Johnstone
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