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The finite intersection principle and genericity. (English) Zbl 1375.03046
A FIP degree is a Turing degree that given any computable sequence of subsets of $$\omega$$ computes a maximal subsequence such that the intersection of each finite subcollection is nonempty. Similarly, a 2IP degree computes maximal subsequences such that every pair of sets has nonempty intersection. Suppose that a is a $$\Delta^0_2$$ Turing degree. The authors prove that the following are equivalent: (1) a is FIP, (2) a is 2IP, and (3) a computes a 1-generic set.
This theorem is extended to all Turing degrees by a result of P. Cholak et al. [Trans. Am. Math. Soc. 369, No. 8, 5855–5869 (2017; Zbl 1423.03142)]. For more on the proof theoretic and computable strength of principles related to FIP, see the work of D. D. Dzhafarov and C. Mummert [Isr. J. Math. 196, 345–361 (2013; Zbl 1302.03035)].

##### MSC:
 03D28 Other Turing degree structures 03B30 Foundations of classical theories (including reverse mathematics)
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##### References:
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