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ON CUTS IN ULTRAPRODUCTS OF LINEAR ORDERS II

Published online by Cambridge University Press:  01 May 2018

MOHAMMAD GOLSHANI
Affiliation:
SCHOOL OF MATHEMATICS INSTITUTE FOR RESEARCH IN FUNDAMENTAL SCIENCES (IPM) P.O. BOX:19395-5746TEHRAN, IRANE-mail:[email protected]
SAHARON SHELAH
Affiliation:
EINSTEIN INSTITUTE OF MATHEMATICS THE HEBREW UNIVERSITY OF JERUSALEM JERUSALEM 91904, ISRAEL and DEPARTMENT OF MATHEMATICS RUTGERS UNIVERSITY NEW BRUNSWICK, NJ08854, USAE-mail:[email protected]

Abstract

We continue our study of the class ${\cal C}\left( D \right)$, where D is a uniform ultrafilter on a cardinal κ and ${\cal C}\left( D \right)$ is the class of all pairs $\left( {{\theta _1},{\theta _2}} \right)$, where $\left( {{\theta _1},{\theta _2}} \right)$ is the cofinality of a cut in ${J^\kappa }/D$ and J is some ${\left( {{\theta _1} + {\theta _2}} \right)^ + }$-saturated dense linear order. We give a combinatorial characterization of the class ${\cal C}\left( D \right)$. We also show that if $\left( {{\theta _1},{\theta _2}} \right) \in {\cal C}\left( D \right)$ and D is ${\aleph _1}$-complete or ${\theta _1} + {\theta _2} > {2^\kappa }$, then ${\theta _1} = {\theta _2}$.

Type
Articles
Copyright
Copyright © The Association for Symbolic Logic 2018 

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References

REFERENCES

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