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Topological Ramsey Spaces, Associated Ultrafilters, And Their Applications To The Tukey Theory Of Ultrafilters And Dedekind Cuts Of Nonstandard Arithmetic, Timothy Onofre Trujillo

Electronic Theses and Dissertations

This dissertation makes contributions to the areas of combinatorial set theory, the model theory of arithmetic, and the Tukey theory of ultrafilters. The main results are broken into three parts.

In the first part, we identify some new partition relations among finite trees and use them to answer an open question of Dobrinen; namely, "for n < omega, are the notions of Ramsey for Rn and selective for Rn equivalent?" We show that for each n < omega, it is consistent with ZFC that there exists a selective for Rn ultrafilter which is not Ramsey for Rn.

In the second part, we extend results of Blass concerning Dedekind cuts associated to ultrafilter mappings from p-point and weakly-Ramsey ultrafilters to ultrafilter mappings from Ramsey for R1 ultrafilters. Blass associates to each ultrafilter U on a countable set X and each function g …

Strong Orbit Equivalence And Residuality, Brett M. Werner

Electronic Theses and Dissertations

In this dissertation, we consider notions of equivalence between minimal Cantor systems, in particular strong orbit equivalence. By constructing the systems, we show that there exist two nonisomorphic substitution systems that are both Kakutani equivalent and strongly orbit equivalent. We go on to define a metric on a strong orbit equivalence class of minimal Cantor systems and prove several properties about the metric space. If the strong orbit equivalence class contains a finite rank system, we show that the set of finite rank systems is residual in the metric space. The last result shown is that set of systems with …