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We discuss two constructions for obtaining generically stable Keisler measures in an NIP theory. First, we show how to symmetrize an arbitrary invariant measure to obtain a generically stable one from it. Next, we show that suitable…

Logic · Mathematics 2012-08-14 Pierre Simon

We develop a theory of generically stable and smooth Keisler measures in NIP metric theories, generalizing the case of classical logic. Using smooth extensions, we verify that fundamental properties of (Borel)-definable measures and the…

Logic · Mathematics 2023-10-11 Aaron Anderson

In NIP theories, generically stable Keisler measures can be characterized in several ways. We analyze these various forms of "generic stability" in arbitrary theories. Among other things, we show that the standard definition of generic…

Logic · Mathematics 2020-05-22 Gabriel Conant , Kyle Gannon

We discuss measures, invariant measures on definable groups, and genericity, often in an NIP (failure of the independence property) environment. We complete the proof of the third author's conjectures relating definably compact groups $G$…

Logic · Mathematics 2007-05-23 Ehud Hrushovski , Ya'acov Peterzil , Anand Pillay

We prove a number of results relating the concepts of Keisler measures, generic stability, randomizations, and NIP formulas. Among other things, we do the following: (1) We introduce the notion of a Keisler-Morley measure, which plays the…

Logic · Mathematics 2023-09-04 Gabriel Conant , Kyle Gannon , James E. Hanson

We study one way in which stable phenomena can exist in an NIP theory. We start by defining a notion of 'pure instability' that we call 'distality' in which no such phenomenon occurs. O-minimal theories and the p-adics for example are…

Logic · Mathematics 2015-09-24 Pierre Simon

We investigate Keisler measures in arbitrary theories. Our initial focus is on Borel definability. We show that when working over countable parameter sets in countable theories, Borel definable measures are closed under Morley products and…

Logic · Mathematics 2023-06-28 Gabriel Conant , Kyle Gannon , James Hanson

We study forking, Lascar strong types, Keisler measures and definable groups, under an assumption of $NIP$ (not the independence property), continuing aspects of math.LO/0607442. Among key results are: (i) if $p = tp(b/A)$ does not fork…

Logic · Mathematics 2009-01-29 Ehud Hrushovski , Anand Pillay

We study generically stable measures in the local, NIP context. We show that in this setting, a measure is generically stable if and only if it admits a natural finite approximation.

Logic · Mathematics 2019-09-18 Kyle Gannon

We introduce and investigate the notions of expansiveness, topological stability and persistence for Borel measures with respect to time varying bi-measurable maps on metric spaces. We prove that expansive persistent measures are…

Dynamical Systems · Mathematics 2019-09-26 Pramod Das , Tarun Das

We study some dynamical aspects of the action of automorphisms in model theory in particular in the presence of invariant measures. We give some characterizations for NIP theories in terms of dynamics of automorphisms and invariant measures…

Logic · Mathematics 2022-12-19 Alireza Mofidi

This paper is a modified chapter of the author's Ph.D. thesis. We introduce the notions of sequentially approximated types and sequentially approximated Keisler measures. As the names imply, these are types which can be approximated by a…

Logic · Mathematics 2021-12-13 Kyle Gannon

We introduce the notion of an NTP$_{2}$-smooth measure and prove that they exist assuming NTP$_{2}$. Using this, we propose a notion of distality in NTP$_{2}$ that unfortunately does not intersect simple theories trivially. We then prove a…

Logic · Mathematics 2025-11-25 Itay Kaplan , Pierre Simon

The notion of a complete type can be generalized in a natural manner to allow assigning a value in an arbitrary Boolean algebra B to each formula. We show some basic results regarding the effect of the properties of B on the behavior of…

Logic · Mathematics 2022-01-19 Itay Kaplan , Ori Segel , Saharon Shelah

A relevant thesis is that for the family of complete first order theories with NIP (i.e. without the independence property) there is a substantial theory, like the family of stable (and the family of simple) first order theories. We examine…

Logic · Mathematics 2007-05-23 Saharon Shelah

We develop the theory of generically stable types, independence relation based on nonforking and stable weight in the context of dependent (NIP) theories.

Logic · Mathematics 2008-02-01 Alexander Usvyatsov

We initiate a systematic study of \emph{generic stability independence} and introduce the class of \emph{treeless theories} in which this notion of independence is particularly well-behaved. We show that the class of treeless theories…

Logic · Mathematics 2023-05-30 Itay Kaplan , Nicholas Ramsey , Pierre Simon

We give several characterizations of when a complete first-order theory $T$ is monadically NIP, i.e. when expansions of $T$ by arbitrary unary predicates do not have the independence property. The central characterization is a condition on…

Logic · Mathematics 2026-05-06 Samuel Braunfeld , Michael C. Laskowski

We begin a systematic development of structure theory for a first order theory, which is stable over a monadic predicate. We show that stability over a predicate implies quantifier free definability of types over stable sets, introduce an…

Logic · Mathematics 2023-02-17 Saharon Shelah , Alexander Usvyatsov

We introduce the notion of dependence, as a property of a Keisler measure, and generalize several results of [HPS13] on generically stable measures (in $NIP$ theories) to arbitrary theories. Among other things, we show that this notion is…

Logic · Mathematics 2025-06-09 Karim Khanaki
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