Intermediate predicate logics determined by ordinals

E-ISSN： 1943-5886|55|3|1099-1124

ISSN： 0022-4812

Source： The Journal of Symbolic Logic, Vol.55, Iss.3, 1990-09, pp. : 1099-1124

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Abstract

For each ordinal α > 0, L(α) is the intermediate predicate logic characterized by the class of all Kripke frames with the poset α and with constant domain. This paper will be devoted to a study of logics of the form L(α). It will be shown that for each uncountable ordinal of the form α + η with a finite or a countable η(> 0), there exists a countable ordinal of the form β + η such that L(α + η) = L(β + η). On the other hand, such a reduction of ordinals to countable ones is impossible for a logic L(α) if α is an uncountable regular ordinal. Moreover, it will be proved that the mapping L is injective if it is restricted to ordinals less than ω^ω , i.e. α ≠ β implies L(α) ≠ L(β) for each ordinal α, β ≤ ω^ω .