Lena Ji
Photo by Emily Ji

Lena Ji

Institutional email: lenaji@umich.edu
Permanent email: lenaji.math@gmail.com

Office: 1855 East Hall

Hello! I am an NSF Postdoctoral Fellow at the University of Michigan, mentored by Professor Mircea Mustaţă. I am interested in algebraic geometry and its connections to arithmetic geometry and commutative algebra; in particular, I am interested in Fano varieties, non-algebraically-closed fields, positive characteristic, and rationality.


I received my PhD from Princeton University in 2021 under the supervision of Professor János Kollár. Before that, I was an undergraduate at Columbia University, where I graduated in 2016.

Research (arXiv page):

  1. Symmetries of Fano varieties (with Louis Esser and Joaquín Moraga) (2023). (arXiv)
  2. The fibering genus of Fano hypersurfaces (with Nathan Chen, Benjamin Church, and David Stapleton) (2023). (arXiv)
  3. A threefold violating a local-to-global principle for rationality (with Sarah Frei) (2023). (arXiv)
  4. Rationality of real conic bundles with quartic discriminant curve (with Mattie Ji). Int. Math. Res. Not. IMRN (2023). (journal) (arXiv)
  5. Fano hypersurfaces with no finite order birational automorphisms (with Nathan Chen and David Stapleton) (2022). (arXiv)
  6. Curve classes on conic bundle threefolds and applications to rationality (with Sarah Frei, Soumya Sankar, Bianca Viray, and Isabel Vogt). Accepted by Algebraic Geom. (arXiv)
  7. The Noether–Lefschetz theorem in arbitrary characteristic. Accepted by J. Algebraic Geom. (arXiv)
  8. Structure of geometrically non-reduced varieties (with Joe Waldron). Trans. Am. Math. Soc. 374 (2021), no. 12, 8333–8363. (journal) (arXiv)
  9. Completely controlling the dimensions of formal fiber rings at prime ideals of small height (with Sarah Fleming, S. Loepp, Peter McDonald, Nina Pande, and David Schwein). J. Commut. Algebra 11 (2019) no. 3, 363–388. (journal) (arXiv)
  10. Controlling the dimensions of formal fibers of a unique factorization domain at the height one prime ideals (with Sarah Fleming, S. Loepp, Peter McDonald, Nina Pande, and David Schwein). J. Commut. Algebra 10 (2018), no. 4, 475–498. (journal) (arXiv)


Upcoming travel:

REU advice: Here is my advice for undergraduates on how to apply to REUs.

Formula Morph exhibit at MoMath
Here is a picture of me, as an undergraduate, at the National Museum of Mathematics

Last updated: September 2023.