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 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 کاملDefinability of Initial Segments
Let T be a first order theory formulated in the language L and P a new relation symbol not in L. Let φ(P ) be an L ∪ {P}-sentence. Let us say that φ(P ) defines P implicitly in T if T proves φ(P ) ∧ φ(P ) → ∀x(P (x) ↔ P (x)). Beth’s definability theorem states that if φ(P ) defines P implicitlly in T then P (x) is equivalent to an L-formula. However, if we consider implicit definability in a gi...
متن کامل2 5 Ja n 20 09 Lattice Initial Segments of the Turing Degrees Copyright Fall 2002
Lattice Initial Segments of the Turing Degrees
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Pacific Journal of Mathematics
سال: 1968
ISSN: 0030-8730,0030-8730
DOI: 10.2140/pjm.1968.24.163