MAAGC at GWU 

October 11-12, 2024

The 2024 edition of the Mid-Atlantic Algebra, Geometry, and Combinatorics (MAAGC) Workshop will take place on Friday and Saturday, October 11-12, 2024, at The George Washington University in Washington, DC.

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.


Speakers

Swee Hong Chan (Rutgers University)

Sam Hopkins (Howard University)

Minyoung Jeon (University of Georgia)

Elizabeth Milićević (Haverford College)


Panel discussion

Elizabeth Milićević (Haverford College)

Jingjing Xu (Amazon)

moderated by Jiayuan Wang (Lehigh)


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 George Washington University in downtown Washington, DC.  The campus is easily accessible from the Foggy Bottom station on the Metro's Blue, Silver, and Orange lines; the Farragut North and Dupont Circle stations on the Red line are a 10-15 minute walk.

Friday's lectures will be held in room 302 of the University Student Center, 800 21st St NW.

Saturday's lectures, panel, and poster session will be held in the basement of Phillips Hall, 801 22nd St NW.  

Campus buildings are likely to be locked over the weekend; if you need assistance, please contact the organizers


Schedule

Friday

2:00pm –3:00pm: Elizabeth Milićević (video)

4:00pm –5:00pm: Swee Hong Chan (video)

Saturday

9:00am –10:00am: Minyoung Jeon (video)

11:00am –12:00pm: Sam Hopkins (video)

12:00pm –2:00pm: Lunch Break

2:00pm –3:00pm: Panel on the art of mentorship: being a good mentor and a good mentee

3:30pm–5:00pm: Poster session

Starting at 6:00pm: Social Event 


Abstracts

Swee Hong Chan: Complexity of log-concave inequalities in matroids

A sequence of nonnegative real numbers a_1, a_2, ..., a_n, is log-concave if a_i^2 >= a_{i-1} a_{i+1} for all i ranging from 2 to n-1. Examples of log-concave inequalities range from inequalities that are readily provable, such as the binomial coefficients a_i = \binom{n}{i}, to intricate inequalities that have taken decades to resolve, such as the number of independent sets a_i in a matroid M with i elements (otherwise known as the first Mason's conjecture; and was resolved by June Huh in 2010s in a remarkable breakthrough). It is then natural to ask if it can be shown that the latter type of inequalities is intrinsically more challenging than the former. In this talk, we provide a rigorous framework to answer this type of questions, by employing a combination of combinatorics, complexity theory, and geometry. This is a joint work with Igor Pak. 

Sam Hopkins: Upho posets

A partially ordered set is called upper homogeneous, or “upho,” if every principal order filter is isomorphic to the whole poset. This class of fractal-like posets was recently introduced by Stanley. Our first observation is that the rank generating function of a (finite type N-graded) upho poset is the reciprocal of its characteristic generating function. This means that each upho lattice has associated to it a finite graded lattice, called its core, that determines its rank generating function. With an eye towards classifying upho lattices, we investigate which finite graded lattices arise as cores, providing both positive and negative results. Our overall goal for this talk is to advertise upho posets, and especially upho lattices, which we believe are a natural and rich class of posets deserving of further attention. Essentially no background knowledge will be assumed, and we also hope to highlight several open problems. 

Minyoung Jeon: Mather classes via small resolutions

The Chern-Mather class is a characteristic class, generalizing the Chern class of a tangent bundle of a nonsingular variety to a singular variety. It uses the Nash-blowup for a singular variety instead of the tangent bundle. In this talk, we consider Schubert varieties, known as singular varieties in most cases, in the even orthogonal Grassmannians and discuss the work computing the Chern-Mather class of the Schubert varieties by the use of the small resolution of Sankaran and Vanchinathan with Jones’ technique. We also describe the Kazhdan-Lusztig class of Schubert varieties in Lagrangian Grassmannians, as an analogous result. If time permitted, we discuss the application of Jones’s method on K-orbit closures in flag varieties, as a joint work with Graham and Scott. 

Elizabeth Milićević: Crystal chute moves on pipe dreams 

Schubert polynomials represent a basis for the cohomology of the complete flag variety. In this context, Schubert polynomials are generating functions over various combinatorial objects, such as rc-graphs or reduced pipe dreams.  By restricting Bergeron and Billey’s chute moves on rc-graphs, we define a Demazure crystal structure on the monomials of a Schubert polynomial.  As a consequence, we provide a new method for decomposing Schubert polynomials as sums of key polynomials.  These results complement related work of Assaf and Schilling via reduced factorizations with cutoff, as well as Lenart’s coplactic operators on biwords.  No prior knowledge of either key polynomials or crystals will be assumed in this talk. 


Poster session


Lodging

A block of hotel rooms with a discounted rate is provided by the Club Quarters Washington DC White House, located at 839 17th Street NW, Washington, DC, for Friday night. This hotel is a 10-minute walk from the conference. The discounted rate is $220 / night (including all taxes and fees); you must reserve by September 10 to receive the discounted rate.  Click here to reserve a room.  If you would like to stay a second night at CQ, please reach out to Mridul Trehan at CQ directly.

There are many other hotels in downtown DC near the conference location.  Here are a few possibilities:


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. 


Financial support

There is funding for regional travel and housing, especially for junior participants participating in the poster session. Register by September 10 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.