HALF: Harmonic Analysis and Lean Formalization

ERC Synergy Grant.


HALF

Our goal is to tackle pivotal and long-standing open problems in harmonic analysis, and formalize their proofs in real-time at the University of Bonn.

This shows that it is feasible for mathematicians to verify the correctness of their own proofs.

Challenges in harmonic analysis:

  • Find estimates for multilinear singular integrals;
  • Find new estimates and convergence results for Ergodic averages;
  • Develop nonlinear analogue of Carleson’s theorem.

Our formalization will use Lean and Mathlib.

Team

HALF

Principal Investigators

Postdocs

PhD Students

Visiting Researchers

Student Research Assistants:

  • Alexander Brodbelt Lopez
  • Leo Diedering
  • Evgenia Karunus
  • Pan Lin
  • Felix Pernegger
  • Mara Silge (starting Fall 2026)

Papers and Preprints

  • Formalizing Carleson’s Theorem in Lean, Lars Becker, María Inés de Frutos-Fernández, Leo Diedering, Floris van Doorn, Sébastien Gouëzel, Evgenia Karunus, Edward van de Meent, Pietro Monticone, Jasper Mulder-Sohn, Jim Portegies, Joris Roos, Michael Rothgang, James Sundstrom, Jeremy Tan. arXiv preprint.
  • A blueprint for the formalization of norm-variation of multiple ergodic averages for commuting transformations, Floris van Doorn, Polona Durcik, Joris Roos, Lenka Slavíková, Christoph Thiele. arXiv preprint
  • Weighted Riesz–Kolmogorov criterion and multilinear extrapolation of compactness on variable Lebesgue spaces, Spyridon Kakaroumpas, Stefanos Lappas. arXiv preprint

Jobs

  • We are looking for PhD candidates to join our project! You can apply via the BIGS website (in April or November)
  • We are looking for student research assistants to join the Lean formalization effort. Contact Floris van Doorn if you are interested (only available for students in Bonn).