NOL Seminar with Yanjing Wang
published: 2026-05-07
event date:
2026-05-25
The Nordic Online Logic Seminar
is organised monthly over Zoom, with expository talks on topics of interest for
the broader logic community. The seminar is open for professional or aspiring
logicians and logic aficionados worldwide. If you wish to receive the Zoom ID
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Date Monday, 25 May 2026 at 15:00 CEST (UTC+2) on Zoom
Speaker Yanjing Wang (Professor of Logic, Peking University)
Title Bundled Fragments of First-order Modal Logic
Abstract
First-order modal logic (FOML) provides a natural logical language for reasoning
about modal attitudes, while retaining the richness of quantification for
referring to predicates over domains. However, FOML is notoriously bad
computationally, as most of the useful fragments of the logic are undecidable,
over many model classes. Over the years, only a few fragments (such as the
monodic fragment) have been shown to be decidable under heavy restrictions on
the syntax. In this talk, I survey our recent work on the newly discovered
bundled fragments based on constructions bundling quantifiers and modalities
together. The idea came from our earlier work on epistemic logics of
know-how/why/what, and it led us to many expressive and decidable fragments of
FOML without restricting the number of variables or the arity of the predicates.
I will give an almost complete picture of the (un)decidability of all the basic
bundled fragments of FOML over increasing and constant domain models. I conclude
with some future directions.