Dr. Stephan Ehlen

Professurale Vertretung
Mailing Address
Mathematisches Institut
Universität zu Köln
Weyertal 86-90
50931 Köln
Email: mail [at] stephanehlen.de

Office: Gyrhofstr. 8c, 001 (UG)
Phone: 0221 / 470-5559

Sprechstunde (im SS 18): Montags, 11-12 Uhr.
In der vorlesungsfreien Zeit: nach Vereinbarung.

Stephan Ehlen

Research and Interests

  • Number Theory
  • Modular Forms, Automorphic Forms


  1. On the modular completion of certain generating functions (with K. Bringmann, and Markus Schwagenscheidt), preprint (2018), arXiv
  2. Central L-values of elliptic curves and local polynomials (with P. Guerzhoy, B. Kane, and L. Rolen), submitted (2018), arXiv
  3. Computing Invariants of the Weil representation (with N. P. Skoruppa), in L-Functions and Automorphic Forms (2017, Contributions in Mathematical and Computational Sciences 10, Springer), arXiv
  4. On two arithmetic theta lifts (with Siddarth Sankaran), accepted for publication in Compositio Mathematica, arXiv (2016)
  5. Regularized inner products and errors of modularity (with K. Bringmann and N. Diamantis), (2017, International Mathematics Research Notices), arXiv
  6. Singular moduli of higher level and special cycles, Research in the Mathematical Sciences 2015 2:16, arXiv
  7. Vector valued theta functions associated with binary quadratic forms, Forum Mathematicum 28 (2016), 5, pp. 893-908, arXiv
  8. CM values of regularized theta lifts and harmonic Maass forms of weight one, Duke Math. J., Volume 166, Number 13 (2017), 2447-2519, arXiv
  9. Lattices with many Borcherds products, with J. H. Bruinier and E. Freitag, Math. of. Comp. 85 (2016), 1953-1981 arXiv
  10. Thesis: CM values of regularized theta lifts (2013), tuprints
  11. On CM values of Borcherds products and harmonic weak Maass forms of weight one, preprint (2012), arXiv
  12. Twisted Traces of CM values of weak Maass forms (with C. Alfes), J. Number Theory 133 (2013), no. 6. arXivcomputations
  13. Twisted Borcherds products on Hilbert modular surfaces and the regularized theta lift, Int. J. Number Theory 6 (2010), no. 7, 1473-1489. 


  • Universität zu Köln, Winter 2018/2019: Algebra
  • Universität zu Köln, Summer 2018: Seminar on rational quadratic forms
  • Universität zu Köln, Summer 2018: Lineare Algebra II
  • Universität zu Köln, Winter 2017/2018: Algebra
  • Universität zu Köln, Summer 2017: Mathematik für Lehramtsstudierende II
  • Universität zu Köln, Winter 2016/2017: Mathematik für Lehramtsstudierende I
  • McGill University, Winter 2016: Introduction to modular forms
  • McGill University, Summer 2015: Math 141 - Calculus 2, Mo-Thu, 8:35-10:55, BURN 1B36, myCourses, WebWork
  • McGill University, Fall 2014: Math 223 - Linear Algebra

Conferences and Seminars

Research Seminar Darmstadt-Frankfurt: Superstarrheit und Arithmetizität (SS 13), Arakelov-Theorie (WS 12/13), Selbergs 3/16 Theorem (SS 12)