排序方式: 共有29条查询结果,搜索用时 578 毫秒
1.
Using recursive variants of Baire notions of nowhere dense and meagre sets we study the topological size of speedable and infinitely often speedable functions in a machine-independent framework. We show that the set of speedable functions is not “small” whereas the set of infinitely often speedable functions is “large”. In this way we offer partial answers to a question in [4]. 相似文献
2.
James H. Schmerl 《Mathematical Logic Quarterly》1998,44(4):515-521
There is a recursive set of natural numbers which is the difference set of some recursively enumerable set but which is not the difference set of any recursive set. 相似文献
3.
Geoffrey Laforte 《Mathematical Logic Quarterly》1996,42(1):83-103
In the present paper we prove that the isolated differences of r. e. degrees are dense in the r. e. degrees. Mathematics Subject Classification: 03D25. 相似文献
4.
Abstract
We prove that there are non-recursive r.e. sets
A and C with A <
T
C such that for every set
.
Both authors are supported by “863” and the National
Science Foundation of China 相似文献
5.
《Annals of Pure and Applied Logic》2014,165(7-8):1263-1290
We investigate dependence of recursively enumerable graphs on the equality relation given by a specific r.e. equivalence relation on ω. In particular we compare r.e. equivalence relations in terms of graphs they permit to represent. This defines partially ordered sets that depend on classes of graphs under consideration. We investigate some algebraic properties of these partially ordered sets. For instance, we show that some of these partial ordered sets possess atoms, minimal and maximal elements. We also fully describe the isomorphism types of some of these partial orders. 相似文献
6.
We show that if M is a countable recursively saturated model of True Arithmetic, then G = Aut(M) has nonmaximal open subgroups with unique extension to a maximal subgroup of Aut(M). Mathematics Subject Classification: 03C62, 03C50. 相似文献
7.
Patrizio Cintioli 《Mathematical Logic Quarterly》2011,57(5):517-523
Given a reducibility ?r, we say that an infinite set A is r‐introimmune if A is not r‐reducible to any of its subsets B with |A\B| = ∞. We consider the many‐one reducibility ?m and we prove the existence of a low1 m‐introimmune set in Π01 and the existence of a low1 bi‐m‐introimmune set. 相似文献
8.
Michael Rathjen 《Mathematical Logic Quarterly》1996,42(1):59-66
The paper characterizes the second order arithmetic theorems of a set theory that features a recursively Mahlo universe; thereby complementing prior proof-theoretic investigations on this notion. It is shown that the property of being recursively Mahlo corresponds to a certain kind of β-model reflection in second order arithmetic. Further, this leads to a characterization of the reals recursively computable in the superjump functional. Mathematics Subject Classification: 03F35, 03F15, 03E70. 相似文献
9.
Andrey Bovykin 《Archive for Mathematical Logic》2008,47(6):607-623
In this article we find some sufficient and some necessary -conditions with oracles for a model to be resplendent or chronically resplendent. The main tool of our proofs is internal
arguments, that is analogues of classical theorems and model-theoretic constructions conducted inside a model of first-order
Peano Arithmetic: arithmetised back-and-forth constructions and versions of the arithmetised completeness theorem, namely
constructions of recursively saturated and resplendent models from the point of view of a model of arithmetic. These internal
arguments are used in conjunction with Pabion’s theorem that ensures that certain oracles are coded in a sufficiently saturated
model of arithmetic. Examples of applications are provided for the theories of dense linear orders and of discrete linear
orders. These results are then generalised to other ω-categorical theories and theories with a unique countable recursively saturated model.
相似文献
10.
Farzad Didehvar 《Mathematical Logic Quarterly》1999,45(4):467-470
We define a class of so-called ∑(n)-sets as a natural closure of recursively enumerable sets Wn under the relation “∈” and study its properties. 相似文献