Bill Fei

About me

Hi, I'm Bill! I'm an undergraduate student at Columbia University studying Computer Science. I am broadly interested in deep learning, mechanistic interpretability, and trading/market design.

Some of my past experiences have included an internship in quant finance at Jane Street, mechanistic interpretability research with SPAR, and plasma modeling with Columbia Fusion Research Center. I have also worked/interned at a few crypto startups, including Liquid and at a HIP-3 exchange.

Selected publications

• Crosscoding Through Time: Sparse Feature Discovery Across Sequence Positions
  Dmitry Manning-Coe, Han Xuanyuan, Aniket Deshpande, Andrii Shportko, William Fei
  NeurIPS 2026 (accepted; forthcoming)
• On Shear Alfvén Wave-Induced Fast Ion Losses in Optimized Stellarator Equilibria
  Alexey Romanovich Knyazev, Alexandra Lachmann, Abdullah Syed Hyder, Michael Czekanski, Elizabeth J. Paul, William Fei
  67th Annual Meeting of the APS Division of Plasma Physics, 2025 (meeting abstract)
• FIRM3D: An open-source suite for energetic particle confinement analysis in optimized stellarator equilibria
  Elizabeth J. Paul, Alexey Romanovich Knyazev, Michael Czekanski, William Fei
  67th Annual Meeting of the APS Division of Plasma Physics, 2025 (meeting abstract)

Contact

william [dot] fei [at] columbia [dot] edu