K O I   C O M B I N A T O R I C S   L E C T U R E S

The KOI Combinatorics Lectures is a joint venture between combinatorialists from the Kentucky, Ohio and Indiana area.

The goal of this series of meetings is to foster and build intergenerational friendship and collaboration between researchers broadly defined (graduate students, postdocs, faculty) in the KOI area.

Organizing Committee:
Saúl A. Blanco (IU), Mihai Ciucu (IU), Richard Ehrenborg (UK), Eric Katz (OSU), Margaret Readdy (UK)

The organizers would like to acknowledge The Ohio State University for their generous support.

F A L L   2 0 2 6

Fifth meeting:  October 3, 2026 (in-person)

Location: The Ohio State University, Columbus OH

Local Organizing Committee:
Cesar Cuenca (OSU),  Evan Henning (UK), Nathan Jones (OSU), Eric Katz (OSU), Luke Martin (UK), Ameer Muhialdeen (OSU)

Speakers:  María Angélica Cueto (The Ohio State University), Pavel Galashin (Cornell), Hunter Spink (University of Toronto).

There will also be a Colloquium talk on Friday, October 2, 2026 by Alexander Barvinok (University of Michigan).

Conference Schedule:

Friday, October 2, 2026
03:14 (π time) Colloquium Tea, Math Tower 724 (MW 724)
04:15 - 05:10 pm Colloquium Talk: Alexander Barvinok, "Combinatorial counting, complex analysis and a bit of statistical physics'', Baker Systems Engineering 0144 (BE 0144).
06:00 pm Colloquium Dinner

Saturday, October 3, 2026
All Saturday lectures are held in Cockins Hall 240 (CH 240).  Registration, coffee/tea breaks and the poster session will be held in Math Tower 724 (MW 724).

09:00 - 09:59 am  Arrival/Registration/Meet and Greet/Poster set up time
09:59 - 10:00 am  Welcome, Welcome speech
10:00 - 11:00 am  Hunter Spink, “Quasisymmetric Schubert calculus and the quasisymmetric flag variety"
11:00 - 11:30 am  Coffee Break
11:30 - 12:30 pm  María Angélica Cueto, “Tritangent planes to space sextic curves: a tropical viewpoint"
12:30 - 02:30 pm  Lunch Break
02:30 - 03:14 pm  The KOI Pond Panel
03:14 (π time) - 04:09 pm  Tea Time and the One Picture/One Theorem Poster Session
04:10 - 05:10 pm  Pavel Galashin, "Amplituhedra and origami"
05:11 - 05:20 pm  Conference Photo
06:00 pm -            Conference Dinner

Talk Titles and Abstracts:

Alexander Barvinok, “Combinatorial counting, complex analysis and a bit of statistical physics"

Abstract:  A matching in a graph is a collection of edges such that every vertex is incident to at most one edge of the collection. Let v be the number of vertices of the graph and let d be the maximum degree of a vertex. It turns out that the number of all matchings in the graph, up to a relative error 0 < ε < 1, is determined by the number of matchings with k edges for k = O( √ d̅  ln (v/ε)). We will discuss what the Koebe function has to do with it, and how this is related to the absence of a phase transition in monomer-dimer systems.

María Angélica Cueto, “Tritangent planes to space sextic curves: a tropical viewpoint"

Abstract:  A classical result due to Clebsch from the mid-nineteenth century confirms that every complex space sextic curve (given as an intersection of a quadric and a cubic surface in projective 3-space) has exactly 120 tritangent planes. In this talk we will show how to use combinatorial methods arising from tropical geometry to revisit this classical problem and perform the analogous count over the reals and extensions thereof. This is joint work with Yoav Len, Hannah Markwig and Yue Ren (arXiv:2512.24277 and arXiv:2605.19905).

Pavel Galashin, "Amplituhedra and origami"

Abstract:  I will outline the combinatorial machinery behind a recent proof of the BCFW triangulation conjecture for the amplituhedron. I will mostly focus on the combinatorics of the dimer model on bipartite graphs embedded in a disk, including Kenyon--Smirnov primitives, origami crease patterns, and two punctured versions of planar bipartite graphs related by a surprising combinatorial duality.

Hunter Spink, “Quasisymmetric Schubert calculus and the quasisymmetric flag variety".

Abstract:  Quasisymmetric functions are a stable of algebraic combinatorics. In this talk I will discuss a family of polynomial called "forest polynomials" that interact with a degenerate version of the divided difference operations governing Schubert polynomials. I will also outline the geometry behind this construction.

One Picture One Theorem Poster Session Presenters:

Aidan Dunkelberg, "Divisibility problems in enumeration of matchings"

Evan Henning, "Volumes of consecutively defined sets"

Luke Martin, "Generators of Reduced Ideals in the Dominance Order on Partitions"

Jaewon Min, "Spherical Schubert varieties"

Doel Rivera Laboy, "The scramble number of outerplanar graphs"

Finn Southerland, "A region-sum expression for the characteristic polynomial of hyperplane arrangements"

Parking:

Parking:

Tuttle Garage: 2050 Tuttle Park Pl. Columbus, OH 43210  map

Lane Avenue Garage: 2105 Neil Avenue Columbus, OH 43210  map

Map of all parking garages on campus:  OSU parking map 

Hotel information:

A block of rooms has been reserved at the Springhill Suites, 1421 Olentangy River Road, Columbus, OH 4321.  $139/night.  It is located approximately 2 miles away from OSU.  Phone (614) 297-9912. 

Here is the reservation link.

KOI Lunch List:  Max Kutler's famous lunch list 

Registration:  registration form 

Funding:  The NSF DMS conference grant for the KOI Combinatorics Lectures provides partial funding for participant travel and local costs.  Priority will be placed on funding those individuals to participate who do not have access to other federal support, or who are students, post-doctoral scholars, or from underrepresented groups.  

Funding request form:  funding request form (due September 15, 2026)

Childcare and family care conference resources:  In order to encourage participants whose attendance is contingent in having childcare or family care in place, the NSF has generously provided childcare and family care support.  Please indicate any need when you register.

Pre-registered Participants (so far):

Allan Bagley (University of Kentucky)

Alexander Barvinok (University of Michigan)

Allan Bickle (Purdue University)

Saúl A. Blanco (Indiana University)

Sergei Chmutov (The Ohio State University)

Mihai Ciucu (Indiana University)

María Angélica Cueto (The Ohio State University)

Anakin Dey (The Ohio State University)

Ehren Dolan (University of Tennessee)

Aidan Dunkelberg (Indiana University)

Richard Ehrenborg (University of Kentucky)

Pavel Galashin (Cornell)

Jimmy He (The Ohio State University)

Evan Henning (University of Kentucky)

Chloe Ireland (The Ohio State University)

Nathan Jones (The Ohio State University)

Eric Katz (The Ohio State University)

Gary Kennedy (The Ohio State University)

Marie Kramer (Youngstown State University)

Hai Van Le (North Carolina State University)

Jackson Leaman (University of Kentucky)

Yi Lin (The Ohio State University)

Leonardo de Medeiros (Cornell)

Luke Martin (University of Kentucky)

Rus May (Morehead State University)

Brodie McCuen (Indiana University)

Brian Macdonald (University of Kentucky)

Jaewon Min (University of Illinois at Urbana Champaign)

Adrian Neff (The Ohio State University)

William Newman (The Ohio State University)

Prakod Ngamlamai (The Ohio State University)

Junjie Ni (The Ohio State University)

Margaret Readdy (University of Kentucky)

Doel Rivera Laboy (University of Kentucky)

Finn Southerland (University of Kentucky)

Hunter Spink (University of Toronto)

Julius Tabery (The Ohio State University)

Kumar Vinayak (University of Kentucky)

Jimmy Vineyard (The Ohio State University)

Lok Yam (University of Kentucky)

Zhiyan Ying (The Ohio State University)

Non-discrimination statement and conduct:  The KOI Combinatorics Lectures promotes and encourages a welcoming environment for individuals from all backgrounds.  We actively promote participation from all career stages and from all backgrounds.

Our goal is to foster a wonderful learning community and exchange of ideas.  As per Federal regulations, there is a zero-tolerance policy for discrimination on the basis of race, ethnicity, color, religion, age, national origin, veteran or service status, disability, any other protected category, or identity.  We expect all participants to conduct themselves conscientiously and respectfully. We will not allow harassment or inappropriate behavior. Conference organizers have full discretion to enforce this policy.

If you wish to be added to the KOI Combinatorics Lectures mailing list, please send an e-mail to: koi.combinatorics@gmail.com. 

Last updated:  September 30, 2026