## Stephan Ehlen

Priv.-Doz. Dr. Stephan EhlenUniversity of Cologne

Email: mail@stephanehlen.de

Google Scholar profile

### Research

- Number Theory
- Modular Forms, Automorphic Forms
- LMFDB

### Publications

- CM values of higher automorphic Green functions on orthogonal groups (with Jan H. Bruinier and T. Yang), Invent. Math. (2021), arXiv
- On the modular completion of certain generating functions (with K. Bringmann, and Markus Schwagenscheidt), Int. Math. Res. Not (2021), Issue 8, 6331–6372, arXiv
- Central L-values of elliptic curves and local polynomials (with P. Guerzhoy, B. Kane, and L. Rolen), 2019
*Proc. Lond. Math. Soc.*120 (5), 742-769, arXiv - On two arithmetic theta lifts (with Siddarth Sankaran), 2018,
*Compositio Mathematica*154 (10), 2090-214, arXiv - 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 - Regularized inner products and errors of modularity (with K. Bringmann and N. Diamantis), 2017,
*International Mathematics Research Notices*, arXiv - Vector valued theta functions associated with binary quadratic forms,
*Forum Mathematicum*28 (2016), 5, pp. 893-908, arXiv - CM values of regularized theta lifts and harmonic Maass forms of weight one,
*Duke Math. J.*, Volume 166, Number 13 (2017), 2447-2519, arXiv - Lattices with many Borcherds products, with J. H. Bruinier and E. Freitag,
*Math. of. Comp.*85 (2016), 1953-1981 arXiv - Singular moduli of higher level and special cycles,
*Research in the Mathematical Sciences*2015 2:16, arXiv - Thesis: CM values of regularized theta lifts (2013), tuprints
- Twisted Traces of CM values of weak Maass forms (with C. Alfes),
*J. Number Theory*133 (2013), no. 6. arXiv, computations - On CM values of Borcherds products and harmonic weak Maass forms of weight one, preprint (2012), arXiv
- Twisted Borcherds products on Hilbert modular surfaces and the regularized theta lift,
*Int. J. Number Theory*6 (2010), no. 7, 1473-1489.

### Teaching

- Universität zu Köln, Sommer 2023: Blockseminar zu elementarer Zahlentheorie und Algebra
- Universität zu Köln, Sommer 2022: Seminar zu Post-Quanten-Kryptografie
- Theses / students
- Universität zu Köln, Winter 2020/2021 Lineare Algebra 1
- Universität zu Köln, Sommer 2020: Elliptische Funktionen
- Universität zu Köln, Winter 2019/2020: Zahlentheorie II
- Universität zu Köln, Sommer 2019: Seminar zu Zahlentheorie und Algebra
- Universität zu Köln, Sommer 2019: Algebraische Zahlentheorie (Zahlentheorie I)
- 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

- Arithmetic and Geometric Aspects of Modular Forms, July 22-23, 2019, Oxford, UK
- 2018 Joint meeting of Korean Mathematical Society and the German Mathematical Society, October 3-6, 2018, Seoul, Korea
- ELAZ, September 3-7, 2018 (Organizer with K. Bringmann and P. Moree)
- Building Bridges: 4th EU/US Summer School + Workshop on Automorphic Forms and Related Topics, July 9-20, 2018, Worksheet for the summer shool
- The Bellairs Workshop in Number Theory 2018, Unitary Shimura varieties and modular forms, April 27 - May 4, 2018, Bellairs Research Institute, Holetown, Barbados
- Trends in Modular Forms, December 19-22, 2017, NIMS, Korea
- German-Romanian Mathematics Societies joint meeting, special session on "Automorphic Forms and L-Functions", 16-19 September 2017, Constanta, Romania
- Indefinite theta functions and applications in Physics and geometry, 6-9 June 2017, Trinity College Dublin, Ireland
- Modular forms are everywhere (co-organizer of the summer school), May 15-26, 2017, MPIM Bonn, Germany
- CNTA 2016, June 20-24, 2016, University of Calgary, Alberta, Canada
- LMFDB workshop (Organizer), May 9-12, 2016, AIM, San Jose, CA, USA
- Modular Forms and Moduli Spaces, April 24 - 30, 2016, MFO, Oberwolfach, Germany
- Alberta Number Theory Days VII , June 12-14, 2015 (Banff, AB)
- Automorphic forms: advances and applications, May 25-29, 2015, CIRM, Luminy, France
- Harmonic Maass forms and arithmetic applications, lecture series (w. Yingkun Li), April 2015, KIAS, Seoul, Korea
- The Kudla programme, April 6-10, 2015, CRM, Montreal, Canada
- Number Theory: From Arithmetic Statistics to Zeta elements, September 2014 - April 2015, CRM, Montreal, Canada
- Building Bridges: 2nd EU/US Summer School + Workshop on Automorphic Forms and Related Topics, July 30 - August 11, 2014, Bristol, UK
- LMFDB Workshop, June 2 - 6, 2014, Warwick, UK
- Modular Forms, April 27 - May 3, 2014, MFO, Oberwolfach, Germany
- Heights and Moduli Spaces, June 10-14, 2013, Lorentz Center, Netherlands
- The Bellairs Workshop in Number Theory, May 3-10, 2013, Bellairs Research Institute, Barbados
- Automorphic Forms and L-Functions, March 17-19, 2013, Darmstadt, Germany
- Building Bridges: 1st EU-US conference on Automorphic Forms and related topics, Summer School and Conference, July 30 - August 8, 2012, Aachen, Germany
- Arithmetic geometry of orthogonal and unitary Shimura varieties, June 3-8, 2012, Banff, Canada
- 26th Automorphic Forms Workshop (2012), April 26-29, 2012, Vancouver, Canada
- Symposium:Modular Forms, Mock Theta Functions, and Applications, February 27 - March 3, 2012, Cologne, Germany
- Student Conference on Automorphic Forms, October 11-13, 2011, Darmstadt, Germany
- Explicit theory of automorphic forms, applications and computations, May 9-13, 2011, Centre International de Rencontres Math'ematiques in Luminy, France
- 25th Automorphic Forms Workshop, March 23-26, 2011, Corvallis, OR, USA
- Postech Winter School 2011: Serre's Modularity Conjecture, January 14-21, 2011, Pohang, Korea
- DMV-Studierenkonferenz 2009, October 1-2 2009, Bochum, Germany
- Automorphic Forms and L-functions: Computational Aspects, June 22 - July 3, 2009, Montreal, Canada
- Mock theta functions and applications in combinatorics, algebraic geometry, and mathematical physics, May 25-29, 2009, MPIM Bonn, Germany
- The Bellairs Workshop in Number Theory, May 3-10, 2009, Barbados

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