The Ershov hierarchy

MM Arslanov - Computability in Context: Computation and Logic in the …, 2011 - elibrary.ru
The ershov hierarchy КОРЗИНА ПОИСК НАВИГАТОР ЖУРНАЛЫ КНИГИ ПАТЕНТЫ
ПОИСК АВТОРЫ ОРГАНИЗАЦИИ КЛЮЧЕВЫЕ СЛОВА РУБРИКАТОР Начальная …

Isolation and lattice embeddings

G Wu - The Journal of Symbolic Logic, 2002 - cambridge.org
Say that (a, d) is an isolation pair if a is a ce degree, d is a dce degree, a< d and a bounds all
ce degrees below d. We prove that there are an isolation pair (a, d) and a ce degree c such …

Isolation: motivations and applications

W Guohua, YM Mansurovich - Ученые записки Казанского …, 2012 - cyberleninka.ru
Isolation: motivations and applications – тема научной статьи по математике читайте
бесплатно текст научно-исследовательской работы в электронной библиотеке …

Post's programme for the Ershov hierarchy

B Afshari, G Barmpalias, SB Cooper… - Journal of Logic and …, 2007 - ieeexplore.ieee.org
This article extends Post's; programme to finite levels of the Ershov hierarchy of Δ 2 sets. Our
initial characterization, in the spirit of Post (1994, Bulletin of the American Mathematical …

Bi-isolation in the dce degrees

G Wu - The Journal of Symbolic Logic, 2004 - cambridge.org
In this paper, we study the bi-isolation phenomena in the dce degrees and prove that there
are ce degrees c1< c2 and a dce degree d∈(c1, c2) such that (c1, d) and (d, c2) contain no …

Complementing cappable degrees in the difference hierarchy

R Downey, A Li, G Wu - Annals of pure and applied logic, 2004 - Elsevier
We prove that for any computably enumerable (ce) degree c, if it is cappable in the
computably enumerable degrees, then there is a dce degree d such that c∪ d= 0′ and c∩ …

Bounding computably enumerable degrees in the Ershov hierarchy

A Li, G Wu, Y Yang - Annals of Pure and Applied Logic, 2006 - Elsevier
Lachlan observed that any nonzero dce degree bounds a nonzero ce degree. In this paper,
we study the ce predecessors of dce degrees, and prove that given a nonzero dce degree a …

On the density of the pseudo-isolated degrees

G Wu - Proceedings of the London Mathematical Society, 2004 - cambridge.org
A dce (2-computably enumerable) degree d is pseudo-isolated if d itself is non-isolated (in
the sense that no computably enumerable (ce) degree below d can bound the ce degrees …

[PDF][PDF] The nonisolating degrees are nowhere dense in the computably enumerable degrees

D Cenzer, G LaForte, G Wu - To appear - Citeseer
The dce degrees were first studied by Cooper [5] and Lachlan who showed that there is a
proper dce degree, a dce degree containing no ce sets, and that every nonzero dce degree …

The non-isolating degrees are upwards dense in the computably enumerable degrees

SB Cooper, MC Salts, G Wu - Theory and Applications of Models of …, 2008 - Springer
The existence of isolated degrees was proved by Cooper and Yi in 1995 in [7], where a dce
degree d is isolated by a ce degree a if a< d is the greatest ce degree below d. A computably …