scholarly journals Difference sets and computability theory

1998 ◽  
Vol 93 (1-3) ◽  
pp. 63-72
Author(s):  
Rod Downey ◽  
Zoltán Füredi ◽  
Carl G. Jockusch ◽  
Lee A. Rubel

2008 ◽  
Vol 37 (3) ◽  
pp. 427-435 ◽  
Author(s):  
Yutaka HIRAMINE


2021 ◽  
Vol 71 ◽  
pp. 101795
Author(s):  
Ayça Çeşmelioğlu ◽  
Oktay Olmez


1987 ◽  
Vol 39 (4) ◽  
pp. 1001-1024 ◽  
Author(s):  
Dieter Jungnickel

In this paper we shall be concerned with arcs of divisible semiplanes. With one exception, all known divisible semiplanes D (also called “elliptic” semiplanes) arise by omitting the empty set or a Baer subset from a projective plane Π, i.e., D = Π\S, where S is one of the following:(i) S is the empty set.(ii) S consists of a line L with all its points and a point p with all the lines through it.(iii) S is a Baer subplane of Π.We will introduce a definition of “arc” in divisible semiplanes; in the examples just mentioned, arcs of D will be arcs of Π that interact in a prescribed manner with the Baer subset S omitted. The precise definition (to be given in Section 2) is chosen in such a way that divisible semiplanes admitting an abelian Singer group (i.e., a group acting regularly on both points and lines) and then a relative difference set D will always contain a large collection of arcs related to D (to be precise, —D and all its translates will be arcs).



1999 ◽  
Vol 87 (1) ◽  
pp. 74-119 ◽  
Author(s):  
Ronald Evans ◽  
Henk D.L. Hollmann ◽  
Christian Krattenthaler ◽  
Qing Xiang


2008 ◽  
Vol 73 (3) ◽  
pp. 885-905 ◽  
Author(s):  
Chris J. Conidis

AbstractIn 2004 Csima, Hirschfeldt, Knight, and Soare [1] showed that a set A ≤T 0′ is nonlow2 if and only if A is prime bounding, i.e., for every complete atomic decidable theory T, there is a prime model computable in A. The authors presented nine seemingly unrelated predicates of a set A, and showed that they are equivalent for sets. Some of these predicates, such as prime bounding, and others involving equivalence structures and abelian p-groups come from model theory, while others involving meeting dense sets in trees and escaping a given function come from pure computability theory.As predicates of A, the original nine properties are equivalent for sets; however, they are not equivalent in general. This article examines the (degree-theoretic) relationship between the nine properties. We show that the nine properties fall into three classes, each of which consists of several equivalent properties. We also investigate the relationship between the three classes, by determining whether or not any of the predicates in one class implies a predicate in another class.



2001 ◽  
Vol 7 (1) ◽  
pp. 165-188 ◽  
Author(s):  
Xiang-Dong Hou ◽  
Ka Hin Leung ◽  
Qing Xiang




2008 ◽  
Vol 16 (3) ◽  
pp. 182-190
Author(s):  
Kevin Jennings


2013 ◽  
Vol 20 (1) ◽  
pp. 17-41 ◽  
Author(s):  
Máté Matolcsi ◽  
Imre Z. Ruzsa


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