Junyan Xu
Postdoctoral Researcher at Heidelberg University
Heidelberg, Baden-Württemberg, Germany
Summary
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Rockstar🎓
Top SchoolJunyan Xu is a postdoctoral researcher and PhD mathematician based in Heidelberg, combining 11 years of experience across pure math, machine learning, and formal verification. He has shifted from number theory and algebraic geometry research to hands-on formalization work—currently contributing to Lean's mathlib4 and the formal verification of Fermat's Last Theorem—while previously applying ML to cancer research at the NCI. Junyan’s open-source contributions include synchronizing mathlib4 with the widely used Lean math library, showing deep familiarity with theorem-library engineering and proof refactoring. He is interested in autoformalization and AI-for-mathematics workflows, drawing on practical experience from the Leela Zero deep RL project to envision accessible, dialogue-driven mathematical tools. This blend of rigorous mathematics, ML practice, and proof-assistant engineering positions him to bridge formal theory and scalable AI-assisted formalization.
11 years of coding experience
5 years of employment as a software developer
Doctor of Philosophy - PhD, Mathematics, Doctor of Philosophy - PhD, Mathematics at Indiana University Bloomington
Stackoverflow
103reputation
461reached
0answers
2questions
Github Skills (22)
formal-methods10
mathematics10
proofs10
proof10
math10
maths10
slim10
theorem-proving10
t410
leanback10
git9
automation9
test-automation9
automations9
functional-programming8
Programming languages (14)
Github contributions (5)
leanprover-community/mathlib4
Jan 2023 - Jan 2023
The math library of Lean 4
Role in this project:
Back-end Developer
Back-end DeveloperContributions:1984 reviews, 5 commits, 274 PRs in 21 days
Contributions summary:Junyan primarily contributes to synchronizing the Lean 4 math library (`mathlib4`) with its Lean 3 counterpart, `mathlib3`. This involves porting changes, updating SHA checksums for files, and integrating updates from the upstream mathlib repository. Their contributions center on ensuring consistency and incorporating mathematical definitions and theorems into the Lean 4 environment. Additionally, they are a co-author on multiple commits, showing collaboration in this synchronization effort.
maththeorem-provingcomputer-algebra-systemmathematicsin-progress
leanprover-community/mathlib3
Aug 2020 - Jan 2023
Lean 3's obsolete mathematical components library: please use mathlib4
Role in this project:Back-end Developer
Back-end DeveloperContributions:1314 reviews, 368 commits, 101 PRs in 2 years 5 months
Contributions summary:Junyan primarily contributed to the mathematical components library, `mathlib3`. Their work involved refactoring and fixing existing code, specifically around algebraic structures and topological spaces. They implemented a condition in `exists_nat_pow_near` and proved and made use of equalities to simplify definitions. Their work appears to involve extending or modifying existing mathematical proofs.
maththeorem-provingcomponents-librarymathematicsjavascript
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