The paper introduces a method for controlling multivariate Hawkes-driven stochastic differential equations using machine learning in a non‑Markovian setting. It develops a finite‑dimensional Markovianization technique that approximates Hawkes processes with mixtures of exponential kernels, proving convergence of the approximation to the original process and its value function. A continuous‑time deterministic policy gradient algorithm, called Hawkes‑CT DDPG, is then proposed to solve the control problem model‑free, relying only on observed event times, SDE solutions, and decay filters, and is compared against discrete‑time reinforcement learning approaches for various kernel types.
By Tomasz R. Bielecki, Thibaut Mastrolia, Haoze Yan
The paper introduces a framework for optimal policy improvement in reinforcement learning, defining it as the best single update under given constraints. It shows that restricting improvement to a subset of states is equivalent to solving an induced Markov Decision Process, linking planning with explicit or implicit models to optimal policy improvement. The authors develop a novel operator for greedification under approximate evaluation, demonstrating empirical gains across several RL algorithms and settings.
By Yaniv Oren, Viliam Vadocz, Wiktor Zabka, Thomas Evers, Jan Robine, Wendelin B\"ohmer, Matthijs T. J. Spaan, Martha White, Hendrik Baier, Fenghui Yu
arXiv:2604.01024v2 Announce Type: replace
Abstract: We study model-based learning of finite-window policies in tabular partially observable Markov decision processes (POMDPs). A common approach to le...
By Philip Jordan, Maryam Kamgarpour
Discounted exponential utility provides a principled criterion for risk-sensitive sequential decision-making, but its nonlinear structure complicates reinforcement learning. A recent work \citep{thoppe2026reinforcement} addressed this difficulty by introducing a Bellman-compatible surrogate and two model-free fixed-point algorithms for optimizing it over stationary policies.
arXiv:2607. 17823v1 Announce Type: new Abstract: Reinforcement Learning is a cornerstone technique for modern large reasoning models.
By Riccardo Poiani, Martino Bernasconi, Andrea Celli
arXiv:2607. 03385v1 Announce Type: cross Abstract: Policy learning has received substantial attention with the goal of learning policies from observational data for decision-making.
By Hamsa Bastani, Osbert Bastani, Shihan Chen