MAAGC in NYC 

The 2025 edition of the Mid-Atlantic Algebra, Geometry, and Combinatorics (MAAGC) Workshop will take place on Friday and Saturday, March 21-22, 2025, at the CUNY Graduate Center in New York City.

The MAAGC Workshop aims to bring together senior researchers and junior mathematicians from the region to exchange ideas and forge collaborations in algebra, geometry, and combinatorics. The conference is funded by National Science Foundation grant DMS-2408985.

Registration

Please register here. Registration is free, but helpful for planning purposes (space and refreshments). Junior participants (undergraduate and graduate students as well as postdocs) are encouraged to participate in the poster session. Please include a tentative poster title during registration if you wish to be considered. 

Speakers

Alex Fink (Queen Mary University of London, UK)

Emily Gunawan (University of Massachusetts Lowell)

Eric Ramos (Stevens Institute of Technology)

Eric Rowland (Hofstra University)

Panel discussion: Small talk on giving great talks

Shanshan Ding (Google)

Andrés Muñoz Medina (Google)

Anna Pun (CUNY-Baruch College)

Eric Rowland (Hofstra University)

Organizers

Joel B Lewis (The George Washington University)

Anna Pun (CUNY-Baruch College)

Nicola Tarasca (Virginia Commonwealth University)

Location

The conference will be held at the CUNY Graduate Center in New York City.

Friday's lectures will be held in Rooms 9206/9207.

Saturday's lectures and panel will be held in the Recital Hall, and poster session will be held in the Recital Hall Lobby.

Lodging

If you want to join the room-sharing list, please fill out this form. 

There are many other hotels near the CUNY Graduate Center .  Here are a few possibilities:

• Pod 39 (13 mins walk): use the promo code “podpal” on their website

• Kixby Hotel (3 min walk) 

• Arlo Hotel NoMad (6 mins walk)

• Ace Hotel NYC (8 mins walk)

Schedule

Friday

3:15pm – 3:30am: Check-in

3:30pm – 4:30pm: Alex Fink: Speyer's tropical f-vector conjecture and its proof (video)

5:00pm – 6:00pm: Eric Ramos: Universality theorems for generalized splines (video)

Saturday

10:00am – 10:15am: Check-in 

10:15am – 11:15am: Emily Gunawan: Pattern-avoiding c-Birkhoff polytopes (video)

12:00nn – 1:00pm: Eric Rowland: Combinatorial structure behind Sinkhorn limits (video)

1:00pm – 2:30pm: Lunch Break

2:30pm – 3:30pm: Panel on "Small talk on giving great talks"

3:45pm – 5:30pm: Poster session (Here is the list of poster presenters and poster titles)

Abstracts

Alex Fink: Speyer's tropical f-vector conjecture and its proof 

In 2008, looking to bound the face vectors of tropical linear spaces, Speyer introduced the g-invariant of a matroid. He proved its coefficients nonnegative for matroids representable in characteristic zero and conjectured this in general. After introducing these objects, this talk will give an overview of the ingredients in recent work with Andrew Berget that proves the conjecture.  A main character is the variety of coordinatewise quotients of points in two linear subspaces, and its initial degenerations which encode a new generalization of external activity to a pair of matroids. 

Emily Gunawan: Pattern-avoiding c-Birkhoff polytopes 

There is a bijection between type A Coxeter elements c and type A Dynkin quivers Q. For each type A Coxeter element c, we define a pattern-avoiding Birkhoff subpolytope whose vertices are the permutation matrices of the c-singletons. We show that the (normalized) volume of our polytope is equal to the number of longest chains in a corresponding type A Cambrian lattice. Our work extends a result of Davis and Sagan which states that the volume of the convex hull of the 132 and 312 avoiding permutation matrices is the number of longest chains in the Tamari lattice, a special case of a type A Cambrian lattice. Furthermore, we prove that each of our polytopes is unimodularly equivalent to the (Stanley’s) order polytope of the heap H of the longest c-sorting word. The Hasse diagram of H is given by the Auslander—Reiten quiver for the quiver representations of Q. This talk is based on joint work with Esther Banaian, Sunita Chepuri, and Jianping Pan. 

Eric Ramos: Universality theorems for generalized splines 

We study generalized splines from the perspective of the representation theory of the category of graphs with contractions. We prove a finite generation result in this context, which implies a kind of universality in the generating set for the module of splines over any graph within a fixed homotopy class. Importantly, these results hold over any Noetherian commutative ring with a chosen finite list of ideals for edge-labels. One can think of our results as expanding upon and explaining many results about generating sets of the module of generalized splines. 

Eric Rowland: Combinatorial structure behind Sinkhorn limits 

The Sinkhorn limit of a positive square matrix is obtained by scaling the rows so each row sum is 1, then scaling the columns so each column sum is 1, then scaling the rows again, then the columns again, and so on. It turns out that the sequence of matrices obtained in this way converges, and the limit has been used for almost 90 years in applications ranging from predicting telephone traffic to machine learning. But until recently, nothing was known about the exact values of its entries. In 2020, Nathanson determined the Sinkhorn limit of a 2 × 2 matrix. Shortly after that, Ekhad and Zeilberger used Gröbner bases to determine the Sinkhorn limit of a symmetric 3 × 3 matrix. Recently, Jason Wu and I determined the Sinkhorn limit of a general 3 × 3 matrix. This was enough to guess the general form for n × n matrices. However, the values of the coefficients that arise are not obvious. We used 1.5 years of CPU time to interpolate formulas from numeric examples, leading to a conjectural determinant formula that reflects new combinatorial structure on sets of minor specifications.

Financial support

There is funding for regional travel and housing, especially for junior participants participating in the poster session. Register by February 28 to receive full consideration for funding for travel and housing. Some funds for childcare are available — please contact the organizers as soon as possible if childcare is requested.