Splitting and Nonsplitting, II: A Low2 C.E. Degree above Which 0' Is Not Splittable
نویسندگان
چکیده
It is shown that there exists a low2 Harrington non-splitting base — that is, a low2 computably enumerable (c.e.) degree a such that for any c.e. degrees x,y, if 0′ = x ∨ y, then either 0′ = x ∨ a or 0′ = y ∨ a. Contrary to prior expectations, the standard Harrington non-splitting construction is incompatible with the low2-ness requirements to be satisfied, and the proof given involves new techniques with potentially wider application.
منابع مشابه
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ورودعنوان ژورنال:
- J. Symb. Log.
دوره 67 شماره
صفحات -
تاریخ انتشار 2002