Jérémy Ledent

IRIF, Université Paris Cité

Bâtiment Sophie Germain

8 Place Aurélie Nemours

75205 Paris Cedex 13

I am currently Maître de Conférences at IRIF, Université Paris Cité.

I was previously a postdoc in the MSP group at the University of Strathclyde. Before that, I completed my PhD at École Polytechnique in the Cosynus team, supervised by Éric Goubault and Samuel Mimram.

Broadly speaking, my research revolves around the formal semantics of concurrent programs. I am particularly interested in methods based on combinatorial topology and epistemic logic.

More generally, my areas of interest include:

Category theory, logic and semantics
Concurrency, Distributed computing
Geometry, (algebraic) topology
Formal languages and automata
λ-calculus, type theory
Game Theory

Selected papers

Epistemic Logic

A Many-Sorted Epistemic Logic for Chromatic Hypergraphs

Éric Goubault, Roman Kniazev, and Jérémy Ledent

Submitted, 2023

Abstract arXiv

We propose a many-sorted modal logic for reasoning about knowledge in multi-agent systems. Our logic introduces a clear distinction between participating agents and the environment. This allows to express local properties of agents and global properties of worlds in a uniform way, as well as to talk about the presence or absence of agents in a world. The logic subsumes previous attempts at epistemic logic with variable number of agents. The semantics is given in chromatic hypergraphs, a generalization of chromatic simplicial complexes, which were recently used to model knowledge in distributed systems. We show that the logic is sound and complete with respect to the intended semantics. We also show a further connection of chromatic hypergraphs with neighborhood frames.
Epistemic Logic,
Topology
Semi-Simplicial Set Models for Distributed Knowledge

Éric Goubault, Roman Kniazev, Jérémy Ledent, and Sergio Rajsbaum

In 38th Annual ACM/IEEE Symposium on Logic in Computer Science (LICS 2023)

Abstract Bibtex URL arXiv Slides More slides

In recent years, a new class of models for multi-agent epistemic logic has emerged, based on simplicial complexes. Since then, many variants of these simplicial models have been investigated, giving rise to different logics and axiomatizations. In this paper, we present a further generalization, which encompasses all previously studied variants of simplicial models. Geometrically, this is achieved by generalizing beyond simplicial complexes, and considering instead semi-simplicial sets. By doing so, we define a new semantics for epistemic logic with distributed knowledge, where a group of agents may distinguish two worlds, even though each individual agent in the group is unable to distinguish them. As it turns out, these models are the geometric counterpart of a generalization of Kripke models, called “pseudo-models”. We show how to recover the previously defined variants of simplicial models as sub-classes of our models; and give a sound and complete axiomatization for each of them.
```
@inproceedings{GoubaultKLR23semisimplicial,
  author       = {{\'{E}}ric Goubault and
                  Roman Kniazev and
                  J{\'{e}}r{\'{e}}my Ledent and
                  Sergio Rajsbaum},
  title        = {Semi-Simplicial Set Models for Distributed Knowledge},
  booktitle    = {38th Annual ACM/IEEE Symposium on Logic in Computer Science (LICS)},
  pages        = {1–13},
  year         = {2023},
  url          = {https://doi.org/10.1109/LICS56636.2023.10175737},
  doi          = {10.1109/LICS56636.2023.10175737},
}
```