On the diophantine equation
Li Yu, Maohua Le (1995)
Acta Arithmetica
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Li Yu, Maohua Le (1995)
Acta Arithmetica
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Paul Erdös, Steve Jackson, R. Mauldin (1994)
Fundamenta Mathematicae
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We consider a set, L, of lines in and a partition of L into some number of sets: . We seek a corresponding partition such that each line l in meets the set in a set whose cardinality has some fixed bound, . We determine equivalences between the bounds on the size of the continuum, , and some relationships between p, and .
M. Kühleitner, W. G. Nowak, J. Schoissengeier, T. D. Wooley (1998)
Acta Arithmetica
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The arithmetic function counts the number of ways to write a natural number n as a sum of two kth powers (k ≥ 2 fixed). The investigation of the asymptotic behaviour of the Dirichlet summatory function of leads in a natural way to a certain error term which is known to be in mean-square. In this article it is proved that as t → ∞. Furthermore, it is shown that a similar result would be true for every fixed k > 3 provided that a certain set of algebraic numbers contains a...
Maohua Le (1995)
Acta Arithmetica
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Bjorn Poonen (1998)
Acta Arithmetica
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Péter Komjáth (1998)
Fundamenta Mathematicae
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It is consistent that but .
Witold Marciszewski (1997)
Fundamenta Mathematicae
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We construct two examples of infinite spaces X such that there is no continuous linear surjection from the space of continuous functions onto × ℝcp(X)cp(X). One of these examples is compact. This answers some questions of Arkhangel’skiĭ.
Michał Sierakowski (1999)
Fundamenta Mathematicae
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E. C. Zeeman [2] described the behaviour of the iterates of the difference equation , n ≥ k, R,Q polynomials in the case and , positive, α nonnegative. We generalize his results as well as those of Beukers and Cushman on the existence of an invariant measure in the case when R,Q are affine and k = 1. We prove that the totally invariant set remains residual when the coefficients vary.
A. Hajnal, Istvan Juhász, Saharon Shelah (2000)
Fundamenta Mathematicae
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The relations M(κ,λ,μ) → B [resp. B(σ)] meaning that if with |A|=κ is μ-almost disjoint then A has property B [resp. has a σ-transversal] had been introduced and studied under GCH in [EH]. Our two main results here say the following: Assume GCH and let ϱ be any regular cardinal with a supercompact [resp. 2-huge] cardinal above ϱ. Then there is a ϱ-closed forcing P such that, in , we have both GCH and [resp. for all . These show that, consistently, the results of [EH] are sharp....
Juan Martínez (1999)
Fundamenta Mathematicae
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It was proved by Juhász and Weiss that for every ordinal α with there is a superatomic Boolean algebra of height α and width ω. We prove that if κ is an infinite cardinal such that and α is an ordinal such that , then there is a cardinal-preserving partial order that forces the existence of a superatomic Boolean algebra of height α and width κ. Furthermore, iterating this forcing through all , we obtain a notion of forcing that preserves cardinals and such that in the corresponding...
R. Grant Woods (1995)
Fundamenta Mathematicae
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It is shown that associated with each metric space (X,d) there is a compactification of X that can be characterized as the smallest compactification of X to which each bounded uniformly continuous real-valued continuous function with domain X can be extended. Other characterizations of are presented, and a detailed study of the structure of is undertaken. This culminates in a topological characterization of the outgrowth , where is Euclidean n-space with its usual metric. ...
Sakaé Fuchino, Lajos Soukup (1997)
Fundamenta Mathematicae
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We introduce a very weak version of the square principle which may hold even under failure of the generalized continuum hypothesis. Under this weak square principle, we give a new characterization (Theorem 10) of partial orderings with κ-Freese-Nation property (see below for the definition). The characterization is not a ZFC theorem: assuming Chang’s Conjecture for , we can find a counter-example to the characterization (Theorem 12). We then show that, in the model obtained by adding...
Saharon Shelah, Juris Steprans (1994)
Fundamenta Mathematicae
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It is shown to be consistent that every function of first Baire class can be decomposed into continuous functions yet the least cardinal of a dominating family in is . The model used in the one obtained by adding Miller reals to a model of the Continuum Hypothesis.
Pingzhi Yuan, Jiabao Wang (1998)
Acta Arithmetica
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Krzysztof Barański (1995)
Fundamenta Mathematicae
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We study the Julia sets for some periodic meromorphic maps, namely the maps of the form where h is a rational function or, equivalently, the maps . When the closure of the forward orbits of all critical and asymptotic values is disjoint from the Julia set, then it is hyperbolic and it is possible to construct the Gibbs states on J(˜f) for -α log |˜˜f|. For ˜α = HD(J(˜f)) this state is equivalent to the ˜α-Hausdorff measure or to the ˜α-packing measure provided ˜α is greater or smaller...
Tamás Keleti (1998)
Fundamenta Mathematicae
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We investigate some problems of the following type: For which sets H is it true that if f is in a given class ℱ of periodic functions and the difference functions are in a given smaller class G for every h ∈ H then f itself must be in G? Denoting the class of counter-example sets by ℌ(ℱ,G), that is, , we try to characterize ℌ(ℱ,G) for some interesting classes of functions ℱ ⊃ G. We study classes of measurable functions on the circle group that are invariant for changes on null-sets...
Dale Alspach (1997)
Fundamenta Mathematicae
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It is shown that if α,ζ are ordinals such that 1 ≤ ζ < α < ζω, then there is an operator from onto itself such that if Y is a subspace of which is isomorphic to , then the operator is not an isomorphism on Y. This contrasts with a result of J. Bourgain that implies that there are uncountably many ordinals α for which for any operator from onto itself there is a subspace of which is isomorphic to on which the operator is an isomorphism.
Sławomir Solecki (2000)
Fundamenta Mathematicae
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We consider two situations which relate properties of filters with properties of the limit operators with respect to these filters. In the first one, we show that the space of sequences having limits with respect to a filter is itself and therefore, by a result of Dobrowolski and Marciszewski, such spaces are topologically indistinguishable. This answers a question of Dobrowolski and Marciszewski. In the second one, we characterize universally measurable filters which fulfill Fatou’s...
Imre Z. Ruzsa (1996)
Acta Arithmetica
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1. Introduction. A Sidon set is a set A of integers with the property that all the sums a+b, a,b∈ A, a≤b are distinct. A Sidon set A⊂ [1,N] can have as many as (1+o(1))√N elements, hence N/2 sums. The distribution of these sums is far from arbitrary. Erdős, Sárközy and T. Sós [1,2] established several properties of these sumsets. Among other things, in [2] they prove that A + A cannot contain an interval longer than C√N, and give an example that is possible. In [1] they show that...