University of Miami Combinatorics Seminar

Organizers: Bruno Benedetti and Michelle Wachs


When not specified, we meet at 5pm on Mondays, in Ungar Building, Room 402.

Click on the dates for the abstracts.


Spring 2023

January 30: Michelle Wachs (U Miami), On q-unimodality of generalized Gaussian coefficients and LLT polynomials

February 20: Hsin-Chieh Liao (U Miami), Chow rings and augmented Chow rings of uniform matroids and their q-analogs

March 13: Spring Break

April 17: Lisa Seccia (U Genoa), TBA

May 1: Igor Pak (UCLA), Colloquium TBA

Past sessions

Fall 2022

September 19 : Bruno Benedetti (U Miami), Random Simple Homotopy Theory

Thursday, October 6 : Kyle Celano (U Miami), RSK and S_n-action for P-tableaux of 3-free Natural Unit Interval Orders

December 5 : Yuval Roichman (Bar-Ilan U, Israel), Gallai colorings, transitivity and Schur-positivity

Spring 2022

February 14 : Richard Stanley (U Miami, MIT), A Fibonacci Analogue of Pascal's Triangle

February 21 : Bruno Benedetti (U Miami), Vertex Labeling Properties for Simplicial Complexes

February 28 : Marta Pavelka (U Miami), 2-LC triangulated manifolds are exponentially many

March 7 : Kyle Celano (U Miami), Geometric Bases of Hessenberg Varieties and the Stanley-Stembridge Conjecture

March 14 : Mark Skandera (Lehigh U), Symmetric generating functions and permanents of totally nonnegative matrices

March 21: no seminar

March 28: Hsin-Chieh Liao (U Miami), Stembridge codes, Chow rings of Boolean matroids, and their extensions

April 4: no seminar

April 11: no seminar due to Faculty Senate Awards

April 18: no seminar due to department meeting

April 25: Michelle Wachs (U Miami), On an n-ary generalization of the Lie representation

Spring 2020

February 11 (Tuesday 5PM): Richard Stanley (U Miami, MIT), Persification

February 17: Carly Klivans, (Brown U), Flow-firing processes

February 24: Matteo Varbaro (U Genova, Italy), Square-free Gr?bner degenerations

March 2: Mark Skandera (Lehigh U), Generating functions for induced characters of the hyperoctahedral group

March 9: Spring Break

March 30: Rafael González D'León (Sergio Arboleda U, Colombia), TBA

Spring 2019

January 22: Emanuele Delucchi (U Fribourg, Switzerland), Stanley-Reisner rings of symmetric simplicial complexes

February 4: Eric Katz (Ohio State), The Unipotent Torelli Theorem for Graphs

February 18: Francesco Brenti (U Roma 2, Italy), Permutations, tensor products, and Cuntz algebra automorphisms

February 25: Marta Pavelka (UM), On a paper by Delucchi and Hoessly

February 28 (Colloquium): Sergey Fomin (U Michigan)

March 25: Fabrizio Zanello (MTU), On the parity of the partition function

April 8: Rafael González D'León (Sergio Arboleda U, Colombia)

April 22: Morgan Brown (UM)

April 29: Federico Castillo (U Kansas)

Fall 2018

September 24: José Alejandro Samper (UM), Round polytopes

October 1: Bruno Benedetti (UM), Random preprocessing in computational topology

October 8: Alex Lazar (UM), On the Intersection Lattice of the Homogenized Linial Arrangement

October 15: Amzi Jeffs (U Washington), Convex Union Representability of Simplicial Complexes

October 29: Joseph Doolittle (Kansas U), Reconstructing Spheres and Polytopes

November 12: Alejandro Ginory (Rutgers), Positivity Conjectures for Jack Polynomials

December 3 (4pm in UB 506): Zvi Rosen (Florida Atlantic University), Combinatorial Neural Codes


January 22: Richard Stanley (U Miami & MIT), The Sperner property

January 29: Jai Aslam (Northeastern), Intersection patterns of sets

February 5: Bruno Benedetti (U Miami), Some contractible 2-complexes do not embed in R^4

February 19: Michelle Wachs (U Miami), On enumerators of Smirnov words by descents and by cyclic descents

March 5: Jessica Striker (North Dakota State U), Sign matrix polytopes

March 19: José Alejandro Samper (U Miami), Threshold hypergraphs revisited

March 27: Tue. 5PM (dissertation defense) Brittney Ellzey (U Miami), The chromatic quasisymmetric function of directed graphs

April 3: Tue. 5PM (colloquium) Fu Liu (UC Davis), Ehrhart Positivity

April 9: Bruno Benedetti (U Miami), Parity arguments in combinatorics and beyond

April 16: Felix Gotti (UC Berkeley), A connection between tilings and matroids on the lattice points of a regular simplex

April 23: Alex Lazar (UM), The Homogenized Linial Arrangement

April 30: Takayuki Hibi (Osaka U), TBA

FALL 2017

August 21: José Alejandro Samper (U Miami), Hopf Algebras in Combinatorics

August 28: José Alejandro Samper (U Miami), Hopf Algebras in Combinatorics

September 4: Labor Day

September 11: Brittney Ellzey (U Miami), CANCELLED DUE TO IRMA

September 11: James McKeown (U Miami), CANCELLED DUE TO IRMA

September 18: José Alejandro Samper (U Miami), CANCELLED DUE TO IRMA

September 25: Tiago Novello de Brito (Pontifícia Universidade Católica do Rio de Janeiro), Discrete Line Field

October 9: MSRI workshop, no seminar this week

October 16: José Alejandro Samper (U Miami), Hopf Algebras in Combinatorics

October 23: Manuel Rivera (U Miami), A combinatorial model for the based loop space

October 30: Brittney Ellzey (U Miami), Chromatic quasisymmetric functions of directed graphs

November 6: Michelle Wachs (U Miami), Chromatic quasisymmetric functions and Hessenberg varieties

November 13: James McKeown (U Miami), Tilings of Space and the Dedekind-MacNeille completion of Bruhat order

November 20: Thanksgiving break, no seminar this week

December 4: José Alejandro Samper (U Miami), Hopf Algebras in Combinatorics

December 11: José Alejandro Samper (U Miami), Hopf Algebras in Combinatorics

December 18: José Alejandro Samper (U Miami), Hopf Algebras in Combinatorics



January 23: Richard Stanley (U Miami & MIT), Counting with congruence conditions

January 30: Bruno Benedetti (U Miami), Mogami constructions of manifolds from trees of tetrahedra

February 6: José Samper Casas (UM), On conjectural relatives of matroid polytopes

February 13: Brittney Ellzey (UM), A directed graph generalization of chromatic quasisymmetric functions

February 17, 4pm: Sebi Cioaba (U Delaware), Simplicial rook graphs: algebraic and combinatorial properties

February 20: Hai Long Dao (U Kansas), On local-global phenomena in the Betti tables of Stanley-Reisner ideals

February 27: Yuval Roichman (Bar-Ilan U, Israel), Cyclic descents of standard Young tableaux

February 28 Tue., 5PM (colloquium): Ron Adin (Bar-Ilan U, Israel), Cyclic descents, toric Schur functions and Gromov-Witten invariants

March 6: Laura Escobar (Urbana Champaign), Rhombic tilings and Bott-Samelson varieties

March 7 Tue., 5PM (colloquium): Anders Björner (KTH, Sweden), Around codimension one embeddings

March 13: Spring break

March 20: Fabrizio Zanello (Michigan Tech), Partition into distinct parts and unimodality

March 27: Tewodros Amdeberhan (Tulane), Determinants in "Wonderland"

April 3: Felix Gotti (UC Berkeley), Dyck paths and positroids from unit interval orders

April 10: Passover (no seminar this week)

April 17: Michelle Wachs (U Miami), On r-inversions and symmetric functions

April 24: Vasu Tewari (U Washington), Labeled binary trees, Schur-positivity and generalized Tamari lattices


FALL 2016

August 29: Hailun Zheng (U Washington), A characterization of simplicial manifolds with g2 ≤ 2

September 5: Labor day (no seminar this week)

September 12: Jay Yang (U Wisconsin-Madison), Random toric surfaces and a threshold for smoothness

September 19: Alessio Sammartano (Purdue), Blowup algebras of rational normal scrolls

September 24-26: AMS Sectional meeting (Maine), no seminar this week

October 3: Nancy Abdallah (Linkoeping U, Sweden), Bruhat order on twisted identities and KLV polynomials

October 6 (Colloquium): Frank H. Lutz (TU Berlin, Germany), On the Topology of Steel

-- canceled due to hurricane Matthew

October 17: Anastasia Chavez (UC Berkeley), The Dehn-Sommerville relations and the Catalan matroids

October 24: Rainer Sinn (Georgia Tech), Positive semidefinite matrix completion and free resolutions

October 31: Katharina Jochemko (TU Wien, Austria), Discrete vs. continuous valuations: similarities and differences

November 7: Alex Lazar (UM), Filtered geometric lattices

November 14: John Shareshian (Washington U.), Subrack lattices of group racks

November 21: Jim Haglund (U Penn), LLT polynomials and the chromatic symmetric function of unit interval orders



January 25: Alex Engstr?m (Aalto U, Finland), Boolean Statistics

February 1, 4pm: Richard Stanley (UM & MIT), Parking functions and their generating function. (Please note unusual time)

February 9 (!): Yuval Roichman (Bar-Ilan U, Israel), Geometric grid classes and symmetric sets of permutations

February 15: Matteo Varbaro (U Genova, Italy), Dual graphs and the Castelnuovo-Mumford regularity of subspace arrangements

February 22: ?Russ Woodroofe (Mississippi State), A Broad Class of Shellable Lattices

February 29, 4pm: ?Cynthia Vinzant (North Carolina State U), Real stable polynomials, determinants, and matroids. (Please note unusual time)

March 7: spring break

March 14, 4pm: Mark Skandera (Lehigh U), Evaluations of the power sum traces at Kazhdan-Lusztig basis elements of the Hecke algebra. (Please note unusual time)

March? 17 (!): Emanuele Delucchi (U Fribourg, Switzerland), Toric arrangements and group actions on semimatroids

March 21: Luca Moci (Jussieu-Paris 7, France), Higher dimensional colorings and flows, arithmetic Tutte polynomials, and convolution formulae

March 28: James McKeown (UM), The combinatorics of the Waldspurger decomposition

April 4: Marty Golumbic (U Haifa, Israel), New and Old Graph Dimension Parameters

April 11, 4pm: Efrat Engel Shaposhnik (MIT), Dissertation Defense: Antichains of Interval Orders and Semiorders, and Dilworth Lattices of Maximum Size Antichains

April 18: Brittney Ellzey (UM), The Chromatic Quasisymmetric Function of the Cycle

April 25: Miriam Farber (MIT), Weak Separation, Pure Domains, and Cluster Distance


FALL 2015

September 21: Michelle Wachs (UM), Weighted bond posets and graph associahedra I

September 28: Michelle Wachs (UM), Weighted bond posets and graph associahedra II

October 5: Florian Frick (Cornell), Tverberg-type theorems and zero sum problems

October 12: Ivan Martino (U Fribourg, Switzerland),? Arrangements of subspaces for finite groups and their geometrical applications

October 17-18: AMS sectional meeting (Memphis); no seminar this week

October 26: Bennet Goeckner (Kansas U),? A non-partitionable Cohen-Macaulay complex

November 2: Brittney Ellzey (UM), Power sum expansion of the chromatic quasisymmetric functions

November 10 (!): Jose Samper (U Washington), Relaxations of the matroid axioms.
?5pm, Ungar 402 -? note the change of date!

November 16: Bruno Benedetti (UM), Optimal discrete Morse vectors are not unique.

November 23: Thanksgiving break. Enjoy!

November 30: Barbara Bolognese (Northeastern U, Boston),? Dual graphs of projective curves.

December 7: Carolina Benedetti (Fields Institute and York U, Toronto, Canada): Chromatic symmetric functions on simplicial complexes



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