Who am I

I am both a pure mathematician and an ML practitioner.

Pure Mathematics

Scientifique Collaborateur II at University of Geneva
- Principal Investigator of Ambizione PZ00P2-193324 by Swiss National Science Foundation
Postdoc @ Université d’Angers
Postdoc @ ETH Zürich

Specialize in algebraic geometry. My PhD + Postdoc has been an amazing decade of extended college life working on the frontier of mathematics.

Publications

(2020) with P. Bousseau, S. Guo and L. Wu, Holomorphic anomaly equation for (P², E) and the Nekrasov-Shatashvili limit of local P², Forum of Math., Pi. 9 (2021) e3.
(2019) with L. Wu and F. You, Higher genus relative Gromov–Witten theory and DR-cycles, J. London Math. Soc. 103-4 (2021) 1547–1576.
(2019) with L. Wu, WDVV equation and its application to relative Gromov–Witten theory, Int. Math. Res. Not. (2020), rnz353.

Earlier papers (2015–2018)

2018

with F. You and H.-H. Tseng, Mirror theorems for root stacks and relative pairs, Selecta Math. (N.S.) 25 (2019), no. 4, Paper No. 54, 25 pp.
with Y.-P. Lee, Variations on the theme of quantum Lefschetz, Singularities, mirror symmetry, and the gauged linear sigma model, 171–181, Contemp. Math., 763, Amer. Math. Soc., [Providence], RI, [2021].
with L. Wu and F. You, Structures in genus-zero relative Gromov–Witten theory, J. Topol. 13 (2020), no. 1, 269–307.

2017

with Y.-P. Lee, Towards a quantum Lefschetz hyperplane theorem in all genera, Geom. and Topol. 23-1 (2019), 493–512.
A quantum splitting principle and an application, Ann. Inst. Fourier (Grenoble) 69 (2019), no. 5, 2067–2088.
Chern classes and Gromov–Witten theory of projective bundles, Amer. J. Math.

2016

with Y.-P. Lee, On Gromov–Witten theory of projective bundles, Michigan Math. J. 69 (2020), no. 1, 153–178.

2015

Quantum Leray-Hirsch for toric bundles. Studies quantum D-modules and GKZ systems of toric fibrations. The referee did not want to spend time helping me improve it, so I chose not to publish — the note is available upon request.

Invited talks

Conference & seminar talks (2016–2021)

I don’t record every seminar talk; conference talks tracked since 2018.

2021 — Aug 19–20, introductory Zoom lecture series (4 talks), Chungnam National University.

2019 — Sep 10, Zürich–Beijing Moduli workshop, PKU, Beijing.

2018 — Aug 23, Workshop on Higher Genus Gromov–Witten Invariants, ZJU, Hangzhou.

2017

Dec 28, Winter Young Algebraic Geometer Workshop, SUSTC, Shenzhen.
Oct 27, Algebraic geometry and moduli seminar, ETH Zürich.
May 5, Algebraic geometry and moduli seminar, ETH Zürich.

2016

Nov 28, Geometry and Physics seminar, University of Michigan, Ann Arbor.
Oct 18, Algebraic Geometry seminar, University of California, Santa Barbara.
Sep 15, FRAGMENT seminar, Colorado State University.
Apr 10, AMS Spring Western Sectional Meeting (Special Session), University of Utah.

Teaching

Courses taught (2013–2019)

2019 Spring — Riemann surfaces and Hurwitz theory, ETH Zürich.
2015 Fall — Math 1220 Calculus II, University of Utah.
2014 Fall — Math 1050 College Algebra, University of Utah.
2013 Fall — Math 1050 College Algebra, University of Utah.

All teaching duties above are full lectures throughout the semester (including the PhD period).

Machine Learning

2025 May - 2026 Jul, Research Engineer at Google DeepMind
2023 Dec - 2025 Apr, Founding Engineer at poolside.ai
2021 Oct - 2023 Dec, Research staff at Eleuther AI

Publications

(ICML 2024 spotlight) Stay on topic with Classifier-Free Guidance. G. Sanchez, H. Fan, A. Spangher, E. Levi, S. Biderman.
(ICML 2024) Grokking Group Multiplication with Cosets. D. Stander, Q. Yu, H. Fan, S. Biderman.
(ICLR 2024) YaRN: Efficient Context Window Extension of Large Language Models. B. Peng, J. Quesnelle, H. Fan, E. Shippole.
(ICML 2023 TAGS Workshop) An ML approach to resolution of singularities. G. Bérczi, H. Fan, M. Zeng.
(Genetic Programming Theory & Practice workshop) The OpenELM Library: Leveraging Progress in Language Models for Novel Evolutionary Algorithms. H. Bradley, H. Fan, T. Galanos, R. Zhou, D. Scott, J. Lehman.

Acknowledgments

Eleuther AI is what made all of these above possible at all. In addition, a lot of thanks need to go to Hi-Flyer AI which allowed me to abuse their 10,000-A100 cluster. Also need to thank Google Research Credit and Google TRC project for allowing me to use their amazing VMs and TPU pods.

Contact

Email: me (a) honglu (d) fan
GitHub: github.com/honglu2875