Algebra, Geometry and Combinatorics Day (AlGeCom) is a one day, informal meeting of mathematicians from the University of Illinois, Purdue University, IUPUI, Loyola University Chicago , DePaul University, University of Notre Dame, the University of Michigan and nearby universities, with interests in algebra, geometry and combinatorics (widely interpreted).

Algecom Committee:
Hal Schenck  Alexander Yong  David Speyer Uli Walther Saugata Basu  Evgeny Mukhin Peter Tingley  Chris Drupieski

Date:   March 24, 2018

Location: Department of Mathematics at University of Michigan

Local Organizers (questions related to Algecom 16):
David Speyer

Registration is free. To register, email the local organizer David Speyer at

If you are interested in presenting at the poster session, please e-mail David Speyer at

There is some NSF support (hotel, airfare/car rental) for graduate students to attend.
Interested students should apply by sending to following information to

David Speyer (, by February 15, 2018:

1. Name:
2. Organization:
3. Will you be attending dinner?
4. Brief summary of research interests:
5. Research advisor:
6: Are you interested in presenting at the poster fair?
7. Approximate expenses:

Funding decisions will be made by February 20, 2018.

A block of rooms has been reserved for attendees at the University Inn
(, 734.971.8000,

Please contact the hotel to make your reservations.  This is 1.7 miles from the
conference building. As well as being a pleasant walk, we will
organize carpools from the hotel to the conference, and
bus route four (to conference, [] to the hotel
[]) runs every half hour.

Nearby parking is available in the Forest Parking structure (here is a map).

All talks will be in East Hall 1360.

There will be a poster session in the lower atrium of East Hall.

Dinner will be at Madras Masala at 6:30pm.

9-10: Drew Armstrong (University of Miami)
10:30-11:30 Rebecca Patrias (LaCIM)
2:00-3:00 Nathan Williams (UT Dallas)
3:30-4:30 Alexander Barvinok (U Michigan)
4:30-6 Poster session
6:30-? Dinner at Madras Masala


Coffee and pastries          8-9am 


Drew Armstrong (University of Miami) 9:00-10:00am

The Waldspurger Transform

I will describe work with my graduate student James McKeown. For any nXn "sum-symmetric" matrix M (in which the ith row sum equals the ith column sum) we define an (n-1)X(n-1) matrix WT(M), called its "Waldspurger transform." When M is a permutation matrix, this yields a combinatorial description of a 2005 result of Waldspurger, which decomposes the positive root cone as a strange disjoint union of relatively open cones indexed by partitions. When M is an alternating sign matrix the Waldspurger transform WT(M) describes an order ideal in the "tetrahedral poset." These ideas mostly generalize to type B and provide some hope for a theory of "type B alternating sign matrices."

Rebecca Patrias (LaCIM) 10:30am-11:30am

Title: Promotion on generalized oscillating tableaux and web rotation

Abstract: We introduce the notion of a generalized oscillating tableau and
define a promotion operation on such tableaux that generalizes the classical
promotion operation on standard Young tableaux. As our main application, we
show that this promotion corresponds to rotation of the irreducible
$A_2$-webs of G. Kuperberg.

Lunch       11:30-2:00pm

Nathan Williams (UT Dallas) 2:00-3:00pm

Title: Fixed Points of Parking Functions

Abstract: We define an action of words in [m]^n on R^m to give a new
characterization of parking functions.  We use this viewpoint to give a
simple definition of Gorsky, Mazin, and Vazirani's zeta map when m and n are
coprime, and prove it is invertible.  A specialization recovers Loehr and
Warrington's sweep map on rational Dyck paths.  This is joint work with Jon
McCammond and Hugh Thomas.

Alexander Barvinok   (U Michigan) 3:30-4:30pm

Title: Computing permanents of diagonally dominant matrices and tensors

Abstract: The permanent of an nxn times complex matrix in which the absolute
value of each diagonal entry exceeds the sum of off-diagonal entries in the
same row can be approximated in quasi-polynomial time. The same result holds
for multi-dimensional permanents of tensors. This is an illustration of the
general principle: one can efficiently compute (approximate) a
combinatorially defined polynomial in a complex domain provided the
polynomial has no zeros in a slightly larger domain. As a corollary, we show
how to count perfect matchings in a hypergraph, weighted by their Hamming
distance to a given perfect matching.

Poster session and informal discussions:   4:30-6:00pm


Lunch: There are numerous lunch options within walking distance.


Dinner: 6:30pm  

At Madras Masala


Getting to Ann Arbor:


Childcare:  Parents attending the conference and looking for childcare may
find a useful reference.