منابع مشابه
Lattice Initial Segments of the Turing Degrees
Lattice Initial Segments of the Turing Degrees
متن کاملLocal initial segments of the Turing degrees
Recent results on initial segments of the Turing degrees are presented, and some conjectures about initial segments that have implications for the existence of nontrivial automorphisms of the Turing degrees are indicated. §
متن کاملRepresentation of One-One Degrees by n-Cylindrical Decision Problems
While investigating the one-one equivalence between various general combinatorial decision problems, CLEAVE [l] initated the concept of system functions. System functions are defined on natural numbers and their values are finite sets of natural numbers. They have many properties in common with those arising from GodeI numbering various combinatorial systems such as Turing machines, Markov algo...
متن کاملA note on initial Segments of the Enumeration Degrees
We show that no nontrivial principal ideal of the enumeration degrees is linearly ordered: In fact, below every nonzero enumeration degree one can embed every countable partial order. The result can be relativized above any total degree: If a,b are enumeration degrees, with a total, and a < b, then in the degree interval (a,b), one can embed every countable partial order.
متن کاملThe Gamma question for many-one degrees
A set A is coarsely computable with density r ∈ [0,1] if there is an algorithm for deciding membership in A which always gives a (possibly incorrect) answer, and which gives a correct answer with density at least r. To any Turing degree a we can assign a value ΓT (a): the minimum, over all sets A in a, of the highest density at which A is coarsely computable. The closer ΓT (a) is to 1, the clos...
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ژورنال
عنوان ژورنال: Pacific Journal of Mathematics
سال: 1969
ISSN: 0030-8730,0030-8730
DOI: 10.2140/pjm.1969.29.351