Hostname: page-component-78c5997874-m6dg7 Total loading time: 0 Render date: 2024-11-16T16:11:59.731Z Has data issue: false hasContentIssue false

Finite level Borel games and a problem concerning the jump hierarchy

Published online by Cambridge University Press:  12 March 2014

Harold T. Hodes*
Affiliation:
Cornell University, Ithaca, New York 14853

Extract

The jump hierarchy of Turing degrees assigns to each ξ < (ℵ1)L the degree 0(ξ); we presuppose familiarity with its definition and with the basic terminology of [5]. Let λ be a limit ordinal, λ < (ℵ1)L. The central result of [5] concerns the relation between 0(λ) and exact pairs on Iλ = {0(ξ)ξ < λ}. In [6] this question is raised: Where a is an upper bound on Iλ, how far apart are a and 0(λ)? It is there shown that if λ is locally countable and admissible, they may be very far apart: 0(λ) = the least member of {a(Ind(λ))∣, a is an upper bound on Iλ}; this is rather pathological, for Ind(λ) may be larger than λ. If λ is locally countable but neither admissible nor a limit of admissibles, we are essentially in the case of λ < ; by results of Sacks [12] and Enderton and Putnam [2], 0(λ) = the least member of {a(2)a is an upper bound on Iλ}. If λ is not locally countable, Ind(λ) is neither admissible nor a limit of admissibles, so we are again in a case like that of λ < . But what if λ is locally countable and nonadmissible, but is a limit of admissibles? For the rest of this paper let λ be such an ordinal. The central result of this paper answers this question for some such λ.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 1984

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

[1]Davis, Morton, Infinite games with perfect information, Advances in game theory, Annals of Mathematics Studies, no. 52, Princeton University Press, Princeton, New Jersey, 1964, pp. 85101.Google Scholar
[2]Enderton, H. B. and Putnam, Hilary, A note on the hyperarithmetical hierarchy, this Journal, vol. 35 (1970), pp. 429430.Google Scholar
[3]Friedman, Harvey, Higher set theory and mathematical practice. Annals of Mathematical Logic, vol. 2 (1971), pp. 325357.CrossRefGoogle Scholar
[4]Hodes, Harold T., Jumping through the transfinite, Ph.D. Thesis, Harvard University, Cambridge, Massachusetts, 1977.Google Scholar
[5]Hodes, Harold T., Jumping through the transfinite, this Journal, vol. 45 (1980), pp. 204220.Google Scholar
[6]Hodes, Harold T., Upper bounds on locally countable admissible initial segments of a Turing degree hierarchy, this Journal, vol. 46 (1981), pp. 753760.Google Scholar
[7]Jensen, Ronald, The fine structure of the constructible hierarchy, Annals of Mathematical Logic, vol. 4 (1972), pp. 229308.CrossRefGoogle Scholar
[8]Jockusch, Carl Jr., and Simpson, Stephen, A degree-theoretic definition of the ramified analytical hierarchy, Annals of Mathematical Logic, vol. 10 (1976), pp. 132.CrossRefGoogle Scholar
[9]Martin, Donald, Borel determinacy, Annals of Mathematics, ser. 22, vol. 102(1975), pp. 363371.CrossRefGoogle Scholar
[10]Martin, Donald, Analysis and Σ40 games (unpublished manuscript).Google Scholar
[11]Moschovakis, Yiannis, Elementary induction on abstract structures, North-Holland, Amsterdam, 1974.Google Scholar
[12]Sacks, Gerald, Forcing with perfect closed sets, Axiomatic set theory. Proceedings of Symposia in Pure Mathematics, vol. 13, part 1, American Mathematical Society, Providence, Rhode Island, 1971, pp. 331355.CrossRefGoogle Scholar