We cordially invite you to attend the KSE Mathematics Seminar on the topic: “Connecting matrices and plabic graphs”!

Speaker: Olha Shevchenko (PhD student, University of California, Los Angeles).

The event will take place on December 17, from 16:30 to 17:30, at the KSE Dragon Capital Building, Kyiv, 3 Mykhaila Shpaka Street.

Abstract:

In this talk, we will introduce background on the totally nonnegative Grassmannian $Gr_{\geq 0}(k,n)$, a space corresponding to matrices whose maximal minors are all nonnegative. It was shown by Postnikov that points of $Gr_{\geq 0}(k,n)$ can be represented using so-called plabic graphs, allowing for the study of the totally nonnegative Grassmannian and its subspaces combinatorially.

We will also address the following question: Which points of $Gr_{\geq 0}(k,n)$ can be represented by centrally symmetric plabic graphs? I will describe this new space (called totally nonnegative Lagrangian Grassmannian), and outline its algebraic, geometric and combinatorial structure.

About the Speaker:

Olha Shevchenko is a fifth year math grad student at UCLA (Ph.D. in Mathematics expected in 2026), where she previously earned her M.A. She received her Bachelor's degree from V.N.Karazin Kharkiv National University. Her research focuses on algebraic and geometric combinatorics, particularly total positivity and the Lagrangian Grassmannian. She has received several distinctions, including the Balbes Award, the Raymond Redheffer Prize, and a perfect-score gold medal at the European Girls’ Mathematical Olympiad.

Looking forward to seeing you there!