Olivier de Gaay Fortman

École Normale Supérieure de Paris

Département de mathématiques et applications 

École Normale Supérieure de Paris

Address: 45, rue d'Ulm, 75230 Paris Cedex 05 - France 

Office: T17 

Phone: +33 (0)1 44 32 20 41

Email: olivier.de.gaay.fortman at ens.fr

Pictures: one, two

About me 

I am a PhD student under the supervision of Olivier Benoist. I am supported by the European Horizon 2020 program Marie Sklodowska-Curie Co-funding of Regional, National and International Programmes.

My work is in algebraic geometry. In particular, my research involves Hodge theory, real algebraic geometry, algebraic cycles, and moduli spaces.


- Integral Fourier transforms and the integral Hodge conjecture for one-cycles on abelian varieties

Joint with Thorsten Beckmann. 

( arXiv: 2202.05230 )

- Hyperbolic geometry and real moduli of five points on the line 

( arXiv: 2111.06381 )

- Real moduli spaces and density of non-simple real abelian varieties

to appear in The Quarterly Journal of Mathematics

( arXiv: 2008.12976 )


Higher-Dimensional Algebraic Geometry (June 2021 - present) 

Together with Elyes Boughattas, I’m currently organizing a seminar on Mori theory, following Debarre and Kollàr.  

Click here for details and the schedule of the seminar.

Short CV

Current position:

- 2019-present : PhD, École normale supérieur de Paris. PhD advisor: Olivier Benoist.


- 2017-2019 : Master in Mathematics (cum laude), University of Amsterdam. Master thesis advisor: Christopher Lazda. 

- 2014-2017 : Bachelor in Physics and Astronomy, University of Amsterdam.

Notes and talks 

- Contractions of K_X-negative extremal rays: Three examples and a flip (Paris, April 2022)
Stable Reduction of Algebraic Curves (Tatihou, August 2021)

- Noether-Lefschetz Loci and Non-Simple Abelian Varieties over the Real Numbers (Tel Aviv (online), March 2021)
Courbes Elliptiques, Modularité et le Dernier Théorème de Fermat (ENS, Paris, December 2020)

- Deformations of Singularities (Amsterdam (online), November 2020)

- La finitude du nombre de classes d’un groupe algébrique linéaire (ENS, Paris, March 2020)

- o-Minimal structures in algebraic geometry (Freiburg, September 2019)

- Torsors under finite locally free group schemes in characteristic p (Master Thesis, July 2019)

Teaching 2022

Complex Analysis

École Normale Supérieure de Paris

Assistant Teacher 

Fall 2022

Teaching 2020

Elliptic Curves (Teacher, 2020) 

Groupe de travail sur les Courbes Elliptiques

M1, ENS Paris, Autumn/Winter 2020 

Teaching 2016-2019

Galois Theory  (Assistant teacher, 2019) 

Geometry (Assistant teacher, 2018) 

Analysis (Assistant teacher, 2018) 

Differential Equations (Assistant teacher, 2017) 

Calculus (Assistant teacher, 2016-2018)