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On finite lattices of degrees of constructibility of reals

Published online by Cambridge University Press:  12 March 2014

Extract

Theorem. Assume that there exists a standard model of ZFC + V = L. Then there is a model of ZFC in which the partial ordering of the degrees of constructibility of reals is isomorphic with a given finite lattice.

The proof of the theorem uses forcing. The definition of the forcing conditions and the proofs of some of the lemmas are connected with Lerman's paper on initial segments of the upper semilattice of the Turing degrees [2]. As an auxiliary notion we shall introduce the notion of a sequential representation of a lattice, which slightly differs from Lerman's representation.

Let K be a given finite lattice. Assume that the universe of K is an integer l. Let ≤ K be the ordering in K. A sequential representation of K is a sequence Ui Ui+1 of finite subsets of ω i such that the following holds:

(1) For any s, s′ Є Ui , i Є ω, k, m Є l, k K m & s(m) = s(m)s(k) = s(k).

(2) For any s Є Ui , i Є ω, s(0) = 0 where 0 is the least element of K.

(3) For any s, s′ Є i Є ω, k,j Є l, if k y Kj = m and s(k) = s(k) & s(j) = s(j)s(m) = s(m), where v K denotes the join in K.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 1976

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References

REFERENCES

[1] Jech, T. J., Lectures in set theory with particular emphasis on the method of forcing, Lecture Notes in Mathematics, vol. 217, Springer-Verlag, Berlin and New York.Google Scholar
[2] Lerman, M., Initial segments of the degrees of unsolvability, Annals of Mathematics, vol. 93 (1971), pp. 365389.CrossRefGoogle Scholar
[3] Lachlan, A. H. and Lebeuf, R., Countable initial segments of the degrees of unsolvability, this Journal, vol. 41 (1976), pp. 289300.Google Scholar
[4] Sacks, G. E., Forcing with perfect closed sets, Axiomatic set theory (Proceedings of Symposia in Pure Mathematics, vol. 13, part I), American Mathematical Society, Providence, R.I., 1971.Google Scholar