Kimoi Kemboi

Instructor in Mathematics
Princeton University

Email: firstname at princeton dot eduOffice: Fine Hall 1107

My research is in algebraic geometry, particularly derived categories and their connections to birational geometry.

Previously, I was a postdoctoral fellow at SLMath (Spring 2024) and a member of the Institute for Advanced Study (Fall 2023). Before that, I was a graduate student at Cornell University, advised by D. Halpern-Leistner.

I am coorganizing the Princeton Algebraic Geometry Seminar.

Portrait of Kimoi Kemboi

Research

A looming of phantoms

Advances in Mathematics 499 (2026), article 111046.

Expand or collapse paper description

We construct new examples of phantom categories in the derived categories of two kinds of rational surfaces: the blowup of the plane at 11 points in general position, and the blowup of the second Hirzebruch surface at nine points in general position. We also propose conjectures for blowups of other Hirzebruch surfaces.

The Fano of lines, the Kuznetsov component, and a flop

Preprint (2025).

Expand or collapse paper description

We prove Galkin's conjecture for cubic fourfolds: the symmetric square of the Kuznetsov component is equivalent to the derived category of the Fano variety of lines. A key ingredient is a derived equivalence for a 12-dimensional flop.

Other writing

Hyperkähler fourfolds and categorical Hilbert squares — Oberwolfach Reports, preliminary report 29/2026.

Talks and expository material

Galkin's conjecture for cubic fourfolds
  • The Fano of lines and the Kuznetsov component of cubic fourfolds, Birational Geometry Seminar, February 2026 (video).
Full exceptional collections and window categories
  • Workshop in Noncommutative Algebraic Geometry, SLMath, Spring 2024 (video).
  • IAS postdoc short talk (video).
  • Fields Medal Symposium, Fields Institute (video).
  • Derived Categories and Moduli Spaces FRG workshop, Cornell University (notes, video).
Semiorthogonal decompositions and geometry
  • A short talk for a general audience, SLMath, Spring 2024 (slides).

Teaching

Current: MAT202 — Linear Algebra with Applications

Course notes

Category theory and homological algebra (PDF).

Waterfall in Ithaca, New York
Ithaca, NY