CXO School is a practitioner-led eight-session pilot for any researcher wondering what their work could lead to, whether that's a spinout, a founding-team role, or a stronger grant or fellowship application. No 'idea' or business background needed.

Wednesdays 1.30–2.30 p.m. from 7 October, Kavli Oxford (South Parks Road). Open to postgraduates, DPhils, researchers and staff. Registration closes 12 p.m., Monday 5 October.

The fiber of multiparameter persistent homology for simplicial complexes
Harrington, H Tillmann, U Torras-Pérez, M (05 Aug 2026) doi:10.48550/arxiv.2608.04640
Thu, 29 Oct 2026

16:00 - 17:00
L5

Model-Free Policy Gradient for Discrete-Time Mean-Field Control

Matthieu Meunier
((Mathematical Institute University of Oxford))
Abstract

We study model-free policy learning for discrete-time mean-field control (MFC) problems with finite state space and compact action space. In contrast to the extensive literature on value-based methods for MFC, policy-based approaches remain largely unexplored due to the intrinsic dependence of transition kernels and rewards on the evolving population state distribution, which prevents the direct use of likelihood-ratio estimators of policy gradients from classical single-agent reinforcement learning. We introduce a perturbation scheme on the state-distribution flow and prove that the gradient of the resulting perturbed value function converges to the true policy gradient as the perturbation magnitude vanishes. This construction yields a model-free estimator based solely on simulated trajectories and an auxiliary estimate of the sensitivity of the state distribution. Building on this framework, we develop MF-REINFORCE, a model-free policy gradient algorithm for MFC, and establish quantitative bounds on its bias and mean-squared error.

We are currently inviting applications for a Postdoctoral Research Associate to work with Professor Terry Lyons at the Mathematical Institute, University of Oxford. These are two-year, fixed-term positions, funded by the Engineering and Physical Sciences Research Council (EPSRC). The starting date of these positions is flexible.

Subscribe to