Despite the growing application of Large Language Models (LLMs) to theoretical physics, there is little academic exploration into how domain-specific physics reasoning ability develops while training these models. To investigate this, we perform the first academic fine-tuning study of small (7B-parameter) reasoning models dedicated specifically to theoretical physics. Because open-source verifiable training data required to train such capabilities is scarce, we developed a robust data generation pipeline that can both create synthetic problems and make existing human-authored problems suitable for model training. Selecting Quantum Field Theory (QFT) as our primary domain, we generated over 2,500 synthetic problems alongside a curated collection of human-adapted problems sourced from arXiv and standard pedagogical resources. We conduct both Reinforcement Learning (RL) and Supervised Fine-Tuning (SFT) experiments, benchmarking performance gains as well as generalization to other physics domains. We perform an extensive analysis of model chains-of-though before and after fine-tuning, to understand how reasoning errors evolve during RL and SFT. Finally, we publicly release our data pipeline, verifiable QFT training data, and ∼200M tokens of QFT reasoning traces.
@article{arxiv.2604.18936,
title = {Fine-Tuning Small Reasoning Models for Quantum Field Theory},
author = {Nathaniel S. Woodward and Zhiqi Gao and Yurii Kvasiuk and Kendrick M. Smith and Frederic Sala and Moritz Münchmeyer},
journal= {arXiv preprint arXiv:2604.18936},
year = {2026}
}