ترغب بنشر مسار تعليمي؟ اضغط هنا

A model with no magic sets

355   0   0.0 ( 0 )
 نشر من قبل Shelah Office
 تاريخ النشر 1998
  مجال البحث
والبحث باللغة English




اسأل ChatGPT حول البحث

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 f[X]=[0,1]. In particular in this model there is no magic set, i.e., a set M subseteq R such that the equation f[M]=g[M] implies f=g for every continuous nowhere constant functions f,g:R-> R .



قيم البحث

اقرأ أيضاً

97 - John T. Baldwin 2021
Let $M$ be strongly minimal and constructed by a `Hrushovski construction. If the Hrushovski algebraization function $mu$ is in a certain class ${mathcal T}$ ($mu$ triples) we show that for independent $I$ with $|I| >1$, ${rm dcl}^*(I)= emptyset$ (* means not in ${rm dcl}$ of a proper subset). This implies the only definable truly $n$-ary function $f$ ($f$ `depends on each argument), occur when $n=1$. We prove, indicating the dependence on $mu$, for Hrushovskis original construction and including analogous results for the strongly minimal $k$-Steiner systems of Baldwin and Paolini 2021 that the symmetric definable closure, ${rm sdcl}^*(I) =emptyset$, and thus the theory does not admit elimination of imaginaries. In particular, such strongly minimal Steiner systems with line-length at least 4 do not interpret a quasigroup, even though they admit a coordinatization if $k = p^n$. The proofs depend on our introduction for appropriate $G subseteq {rm aut}(M)$ the notion of a $G$-normal substructure ${mathcal A}$ of $M$ and of a $G$-decomposition of ${mathcal A}$. These results lead to a finer classification of strongly minimal structures with flat geometry; according to what sorts of definable functions they admit.
Given a finite point set $P$ in the plane, a subset $S subseteq P$ is called an island in $P$ if $conv(S) cap P = S$. We say that $Ssubset P$ is a visible island if the points in $S$ are pairwise visible and $S$ is an island in $P$. The famous Big-li ne Big-clique Conjecture states that for any $k geq 3$ and $ell geq 4$, there is an integer $n = n(k,ell)$, such that every finite set of at least $n$ points in the plane contains $ell$ collinear points or $k$ pairwise visible points. In this paper, we show that this conjecture is false for visible islands, by constructing arbitrarily large finite point sets in the plane with no 4 collinear members and no visible island of size $2^{42}$.
96 - Juan P. Aguilera 2019
It is shown, from hypotheses in the region of $omega^2$ Woodin cardinals, that there is a transitive model of KP + AD$_mathbb{R}$ containing all reals.
Harrington and Soare introduced the notion of an n-tardy set. They showed that there is a nonempty $mathcal{E}$ property Q(A) such that if Q(A) then A is 2-tardy. Since they also showed no 2-tardy set is complete, Harrington and Soare showed that the re exists an orbit of computably enumerable sets such that every set in that orbit is incomplete. Our study of n-tardy sets takes off from where Harrington and Soare left off. We answer all the open questions asked by Harrington and Soare about n-tardy sets. We show there is a 3-tardy set A that is not computed by any 2-tardy set B. We also show that there are nonempty $mathcal{E}$ properties $Q_n(A)$ such that if $Q_n(A)$ then A is properly n-tardy.
126 - Alexander Usvyatsov 2019
We prove that a wide Morley sequence in a wide generically stable type is isometric to the standard basis of an $ell_p$ space for some $p$.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا