Fall 2026

This seminar meets on Fridays 3:00-4:00 PM in Blocker 302.

The organizers are Trevor Karn and Galen Dorpalen-Barry.

Date	Speaker	Title	Other
August 28, 2026			No seminar
September 4, 2026			No seminar
September 11, 2026			No seminar
September 18, 2026			No seminar
September 25, 2026	Frank Sottile (TAMU)	A Littlewood-Richardson Rule for \(2\)-Grassmannian Permutations
October 2, 2026
October 9, 2026	Catherine Yan (TAMU)
October 16, 2026	Charlie Maglund (UW)
October 23, 2026
October 30, 2026			No seminar, SIAM TX-LA Regional Meeting
November 6, 2026
November 13, 2026
November 20, 2026
November 27, 2026			No seminar, Thanksgiving.
December 4, 2026			No seminar, reading day/finals.

Past Semesters

• Spring 2026
• Fall 2025

Related Links

• Texas A&M Geometry Seminar
• Departmental seminar website
• Departmental website of the algebra and combinatorics group (not current!)

Giving a manifestly positive formula for the structure constants arising from the multiplication of two Schubert classes in the cohomology of a flag manifold is a long-standing open problem in algebraic combinatorics. This has only seen limited progress. Most results have restrictions on both classes that are multiplied, and the only formula with a restriction on only one is the Pieri-type formula that is 30 years old. In this talk, I will describe formulas, in both ordinary and equivariant cohomology, for the coefficients that arise when multiplying a Schubert class by one pulled back from a Grassmannian of $2$-planes. This uses geometric constructions including a novel description of certain positroid varieties. The cohomological formula identifies each coefficient as particular Littlewood-Richardson coefficient on a Grassmannian of $k$-planes, for some $k$, not necessarily equal to $2$. This is joint work with Changzheng Li and Mingzhi Yang.

Abstract