Groups and fields with NTP2
Abstract
NTP2 is a large class of first-order theories defined by Shelah and generalizing simple and NIP theories. Algebraic examples of NTP2 structures are given by ultra-products of p-adics and certain valued difference fields (such as a non-standard Frobenius automorphism living on an algebraically closed valued field of characteristic 0). In this note we present some results on groups and fields definable in NTP2 structures. Most importantly, we isolate a chain condition for definable normal subgroups and use it to show that any NTP2 field has only finitely many Artin-Schreier extensions. We also discuss a stronger chain condition coming from imposing bounds on burden of the theory (an appropriate analogue of weight), and show that every strongly dependent valued field is Kaplansky.
Keywords
Cite
@article{arxiv.1212.6213,
title = {Groups and fields with NTP2},
author = {Artem Chernikov and Itay Kaplan and Pierre Simon},
journal= {arXiv preprint arXiv:1212.6213},
year = {2013}
}
Comments
Presentation is improved, some minor mistakes are corrected. Example 5.6 and a new observation concerning Conjecture 5.1 are added. Accepted for publication in the Proceedings of the AMS