Distality Rank
Abstract
Building on Pierre Simon's notion of distality, we introduce distality rank as a property of first-order theories and give examples for each rank such that . For NIP theories, we show that distality rank is invariant under base change. We also define a generalization of type orthogonality called -determinacy and show that theories of distality rank require certain products to be -determined. Furthermore, for NIP theories, this behavior characterizes -distality. If we narrow the scope to stable theories, we observe that -distality can be characterized by the maximum cycle size found in the forking "geometry," so it coincides with -triviality. On a broader scale, we see that -distality is a strengthening of Saharon Shelah's notion of -dependence.
Keywords
Cite
@article{arxiv.1908.11400,
title = {Distality Rank},
author = {Roland Walker},
journal= {arXiv preprint arXiv:1908.11400},
year = {2021}
}
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32 pages