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On the ordering of certain large cardinals1

Published online by Cambridge University Press:  12 March 2014

Carl F. Morgenstern*
Affiliation:
University of California, Santa Cruz, California 95064

Extract

It is well known that the first strongly inaccessible cardinal is strictly less than the first weakly compact cardinal which in turn is strictly less than the first Ramsey cardinal, etc. However, once one passes the first measurable cardinal the inequalities are no longer strict. Magidor [3] has shown that the first strongly compact cardinal may be equal to the first measurable cardinal or equal to the first super-compact cardinal (the first supercompact cardinal is strictly larger than the first measurable cardinal). In this note we will indicate how Magidor's methods can be used to show that it is undecidable whether one cardinal (the first strongly compact) is greater than or less than another large cardinal (the first huge cardinal). We assume that the reader is familiar with the ultrapower construction of Scott, as presented in Drake [1] or Kanamori, Reinhardt and Solovay [2].

Definition. A cardinal κ is huge (or 1-huge) if there is an elementary embedding j of the universe V into a transitive class M such that M contains the ordinals, is closed under j(κ) sequences, j(κ) > κ and jRκ = id. Let κ denote the first huge cardinal, and let λ = j(κ).

One can see from easy reflection arguments that κ and λ are inaccessible in V and, in fact, that κ is measurable in V.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 1979

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Footnotes

1

These results are contained in the author's Ph.D. dissertation prepared at the University of Colorado under the direction of Professor William N. Reinhardt.

References

REFERENCES

[1]Drake, F., Set theory: an introduction to large cardinals, North-Holland, Amsterdam, 1974.Google Scholar
[2]Kanamori, A., Reinhardt, W. and Solovay, R., Strong axioms of infinity and elementary embeddings, Annals of Mathematical Logic, vol. 13 (1978), pp. 73116.Google Scholar
[3]Magidor, M., How large is the first strongly compact cardinal? or: a case study on identity crises, Annals of Mathematical Logic, vol. 10 (1976), pp. 3359.CrossRefGoogle Scholar
[4]Menas, T., On strong compactness and supercompactness, Ph.D. dissertation, University of California, Berkeley, 1973.Google Scholar