Forking and invariant measures in NIP theories
Volume 273 / 2026
Fundamenta Mathematicae 273 (2026), 81-92
MSC: Primary 03C45; Secondary 37B05
DOI: 10.4064/fm250109-17-11
Published online: 11 February 2026
Abstract
We give an example of an NIP theory $T$ in which there is a formula that does not fork over $\varnothing $ but has measure $0$ under any global $\varnothing $-invariant Keisler measure, and we show that this cannot occur if $T$ is also first-order amenable. We also comment on some connections with topological dynamics.
