Goldblatt-Thomason Theorem for Probability Logic

Abstract

Probability logic (PL) extends propositional logic with countably many probability operators, one for each rational number between 0 and 1. The formulas of this logic are interpreted over the class of Markov processes, i.e., structures of the form $(\hat{I}\text{c◯},\hat{I}\pounds ,T)$, where$(\hat{I}\text{c◯},\hat{I}\pounds )$ is a measurable space and $T$ is a Markov kernel. The main contribution of this paper is the establishment of the Goldblatt-Thomason theorem for probability logic. As an application, we show that the class of Harsanyi type spaces is definable in PL. Moreover, we obtain some variants of the Goldblatt-Thomason theorem for specific subclasses of Markov processes.

In Proceedings AiML 2026, arXiv:2606.29444