Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Fall 2009 Schedule

     
August
31 Edward Hanson
A characterization of Leonard pairs in terms of tails
September
7 Labor day
14 Aleksandar Jurisic (U. Ljubljana Slovenia)
The search for new distance-regular graphs 21 Xiaoguang Ma (MIT)
Quantum symmetric pairs and double affine Hecke algebras 28 Martha Yip
A Littlewood-Richardson rule for Macdonald polynomials
October
5 Don Kreher (Mich. Tech)
The degree sequence problem for partial Steiner triple systems 12 David Clark (Mich. Tech)
Designs, geometries, and Hamada's conjecture 19 Seth Meyer
Zero forcing sets 26 Ali Godjali
Thin Hessenberg pairs
November
2 Diana Cerzo
Thin irreducible T-modules for Q-polynomial distance-regular graphs 9 Hiroshi Suzuki (ICU Japan)
Tridiagonal spaces and Leonard pairs 16 Richard Brualdi
Completion of partial matrices to singular/nonsingular matrices 23 Michael Schroeder
Symmetric Hamilton cycle decompositions of graphs 30 Bridget Tenner (DePaul U.)
TBA
December
7 Sergei Sergeev (U. Birmingham UK)
TBA 14 Ales Drapal
Latin bitrades, equilateral triangles and abelian groups

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Spring 2009 Schedule

     
January
26 Paul Terwilliger
The Drinfel'd polynomial of a tridiagonal pair
February
2 Boyd Worawannotai
A Tutte polynomial for signed graphs 9 Diana Cerzo
Imprimitive Q-polynomial schemes 16 Ali Godjali
Properties of graded polynomial sequences and their duals 23 Adam Berliner
The Pesky Permanent Problem
March
2 Mihai Ciucu (U. Indiana)
Random tilings with gaps and electrostatics 9 Zajj Daugherty
Building my favorite centralizer algebras 16 Spring break
23 Richard Brualdi
Potentially nilpotent full sign patterns are spectrally arbitrary - a theorem of R. Pereira 30 Gabriel Pretel
q-geometric tridiagonal pairs and the quantum affine sl2 algebra
April
6 Louis Deaett
The sparse null space basis problem 13 Seth Meyer
Signed edge domination numbers in bipartite graphs 20 (1:20 901 VV) Hajime Tanake (Tohoku U. Sendai)
A bilinear form relating two Leonard systems 20 (2:25 901 VV) Rie Tanake (Tohoku U. Sendai)
Imprimitive Q-polynomial association schemes 27 Mike Schroeder
Latin squares composed of intercalates
May
4 Anna Saputera
Line graphs, root systems, and elliptic geometry 11 (2:00 pm, 901 VV) Boyd Worawannotai
Toward the cyclicly symmetric Askey-Wilson relations for dual polar graphs

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Fall 2008 Schedule

     
September
8 Paul Terwilliger
The classification of tridiagonal pairs of q-Racah type 15 Michael Gekhtman (Notre Dame)
Planar networks, Grassmannians and Poisson structures 22 George Brown
The Smith normal norm and acyclic matrices 29 Aleksandar Jurisic (U. Ljubljana Slovenia)
Distance-regular graphs with light tails
October
6 Michael Lang (Bradley U.)
Entrywise products of pseudo primitive idempotents 13 Plamen Iliev (Georgia Tech.)
Bispectrality of multivariable orthogonal polynomials 20 Bill Martin (WPI)
Lattices, mutually unbiased bases, hemisystems, and Q-polynomial association schemes. 27 Stefko Miklavic (U. Primorska, Slovenia)
The subconstituent algebra of a bipartite distance-regular graph
November
3 Richard Brualdi
Landau's and Rado's Theorems and partial tournaments 10 Louis Deaett
The minimum positive-semidefinite rank of a triangle-free graph 17 Andrei Calderaru
A spectral sequence from the ribbon graph bicomplex 24 Vadim Olshevsky (U. Connecticut)
Quasiseparable matrices and polynomials
December
1 Adam Berliner
TBA 8 Sergei Sergeev (U. Birmingham UK)
Two sided linear systems over max algebra

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Spring 2007 Schedule

     
January
22 Richard Brualdi
Matrix diagonals: something old and something new 24 (1:30, 901VV) Bridget Tenner
Reduced decompositions and permutation patterns 29 Dong-il Lee (Seoul Natl. U.)
Linear algebraic approach to Groebner-Shirshov basis theory
February
5 Amos Ron (U.W. Comp. Sci. Dept.)
Polynomial ideals and polynomial spaces over hyperplane arrangements and zonotopes 12 Stefko Miklavic (U. Ljubljana Slovenia)
Consistent cycles 19 Christoph Schwer
Galleries and q-analogs of symmetric functions 26 Paul Terwilliger
Evaluation modules for the three-point sl2 loop algebra
March
5 Jon Godshall
The q-tetrahedron algebra and the split decomposition of a Leonard Pair 12 (3:30 B131VV) Stefko Miklavic
Leonard triples and the hypercubes 19 Bill Martin (WPI)
Large bounds for binary codes from the subconstituent algebra 26 Kathleen Kiernan
Latin squares with forbidden entries
April
2 Spring break
9 Louis Deaett
Structural properties of triangle-free graphs 16 Lauren Williams (Harvard)
From total positivity on the Grassmanian to the asymmetric exclusion process 23 Mike Schroeder
The m-colored composition poset 30 Melvin Vidar
A family of tridiagonal pairs
May
7 Joohyung Kim
A duality between pairs of split decompositions for a Q-polynomial distance-regular graph 9 (2:25, B333 VV) Helene Barcelo (Arizona State U.)
The discrete fundamental group of the order complex of Bn

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Fall 2006 Schedule

     
September
11 Richard Brualdi
Matrix diagonals 18 Bill Martin (WPI)
An update on (t,m,s)-nets 18 (3:30pm, B341 VV) Alberto Grunbaum (Berkeley)
An ab-initio introduction to the bispectral problem 25 Bill Martin
Design systems: combinatorial characterizations of Delsarte T-designs
October
2 Arjana Zitnik (U. Ljubljana Slovenia)
Triangle-free distance-regular graphs with an eigenvalue multiplicity equal to the valency and diameter three 2 (3:30pm, B341 VV) Aleksandar Jurisic (U. Ljubljana Slovenia)
Characterization of the Patterson graph by its intersection array 9 Paul Hermann Zieschang (U. Brownsville TX)
Recent results and general questions in abstract scheme theory 16 James Parkinson
Iwahori cosets and alcove walks 23 Terry Gannon (U. Alberta CA)
What the trefoil knot can teach modular forms 30 Paul Terwilliger
Distance-regular graphs and the q-tetrahedron algebra
November
6 Claudia Malvenuto, University of Rome, La Sapienza
Pairwise colliding permutations and the capacity of infinite graphs 13 George Brown
Packing densities of layered permutations 20 Joohyung Kim
Characterization of some strongly regular graphs with parameters (64,28, 12, 12) 27 Ales Drapal
Latin trades and surfaces
December
4 (B305 VV) Ashwin Ganesan (U.W. ECE dept.)
Flows in information networks 11 Adam Berliner
Converting the permanent to the determinant

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Spring 2006 Schedule

     
January
23 Paul Terwilliger
The q-tetrahedron algebra 30 Richard Brualdi
Even posets and a parity result of Yaokun Wu
February
6 Susan Hollingsworth
The log-concavity of a famous sequence counting permutations 13 Jin-Yi Cai (UW Comp. Sci. Dept.)
Some results on matchcircuit computations and holographic algorithms 20 Christine Heitsch
Kreweras Complementation and Orbits in Catalan Lattices 27 Arun Ram
The Schur Hopf algebra
March
6 Lev Borisov
Introduction to the Leech lattice 13 Spring break
27 Martin Schlichenmaier (U. Luxembourg)
Higher genus affine Lie algebras of Krichever-Novikov type
April
3 Benjamin Otto
The Lie algebra G2 10 Jon Godshall
The universal central extension of the tetrahedron algebra 17 Han Hyuk Cho
Unicyclic graphs and competition numbers 24 Louis Deaett
Complexity and the structure of low-rank matrices
May
1 Patricia Hersh (U. Indiana)
The q=-1 phenomenon via homology concentration 5 Don Cartwright (U. Sydney, Rutgers) (2:25pm, B333 Van Vleck)
Groups acting simply transitively on the vertices of a building

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Fall 2005 Schedule

     
September
12 Paul Terwilliger
Distance-regular graphs and the quantum affine sl2 algebra 19 David Callan (UW Dept. of Statistics)
Generalizing the Catalan numbers 26 Nigel Boston
Risk and return considerations in The Weakest Link
October
3 Kathrin Bringmann
On mock theta functions and a conjecture of Dragonette and Andrews 10 Richard Brualdi
Latin squares, matroids, partitions, (0,1)-matrices, Young tableaux, graphs, matchings,... 17 Mikhail Klin (Ben Gurion U. Israel)
Links between Latin squares, nets, graphs and groups: work inspired by a paper of A. Barlotti and K. Strambach 24 Etsuko Bannai (Kyushu U. Japan)
On Euclidean designs 31 Sharon Garthwaite
Convolution congruences for the partition congruences
November
7 John Goldwasser (West Virginia U.)
Maximum size antichains and the COLEX order 14 Brian Hartwig
The tetrahedron algebra 21 Jackie Anderson
The largest (s,t)-core partition 28 Dina Christodoulopoul
An introduction to affine Weyl groups
December
5 H.K. Kim (Seoul Natl. U. Korea)
Competition indices of primitive digraphs 12 Louis Deaett
More on the Bruhat order for (0,1)-matrices

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Spring 2005 Schedule

     
January
24 Paul Terwilliger
Bidiagonal triples and the quantum algebra Uq(sl2) 31 Richard Brualdi
Some remarks on the Bruhat order for (0,1) matrices
February
7 Brian Hartwig
Onsager pairs and the Tetrahedron algebra 14 Richard Askey
q-factorial, q-gamma and q-beta functions 21 Nigel Boston
Capacity-achieving graph-based codes 28 Georgia Benkart
A combinatorial tripleheader: lambda-determinants, Schur functions, and perfect matchings
March
7 Christine Heitsch
Random de Bruijn sequences and the design of DNA codewords 14 Adam Berliner
Sidon sequences and magic graphs 21 Spring break
28 Han Cho
Competition graphs and numbers
April
4 Jim Propp
The combinatorics of Markoff numbers 11 Susan Hollingsworth
Cycle decompositions and path packings of K_nn 18 Bret Benesh
A survey of probabilistic group theory 25 Stephan Griffeth
TBA
May
2 Arlene Pascasio (U. De La Salle Philippines)
The pseudo primitive idempotents of a distance-regular graph

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Fall 2004 Schedule

     
September
13 Kyle Petersen (Brandeis)
Descent algebras and P-partitions 20 John Bowman
Symmetric functions and the cohomology of Springer fibers 27 Paul Terwilliger
The compact representation of a Leonard pair
October
4 Cathy Yan (Texas AM)
Noncrossing and nonnesting matchings 11 Richard Brualdi
Perfect Matching Preservers 18 Jaclyn Anderson
A proof of a conjecture of Stanton 25 Karl Mahlburg
A new approach to cranks and ranks
November
1 Jeremy Lovejoy (CNRS)
Extending partition theorems of Schur and Gollnitz to overpartitions 8 Pascal Vontobel
The edge zeta function of graphs and enumerating backtrackless, tailless cycles 15 Stefko Miklavic (Nova Gorica)
Some equitable partitions of Q-polynomial distance-regular graphs 22 Jose Dias da Silva (Lisbon)
Orthogonal dimension of orbital sets 29 Bob Wilson
Rook numbers and the normal ordering problem
December
6 Dina Christodoulopoul
Cluster algebras 13 Arun Ram
Paths, charge and Kostka-Foulkes polynomials

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Spring 2004 Schedule

     
January
26 Dick Askey
A determinant of Sylvester and some extensions
February
2 Stephen Griffeth
Schubert calculus, Hecke algebras, and the Yang-Baxter equation 9 Arun Ram
A new look at the path model 16 Paul Terwilliger
An extension of the quantum affine sl2 algebra 23 Open
March
1 Open
8 Adam Berliner, Rike Bostelmann, Louis Deaett
Sum choice numbers of graphs 15 Spring break
22 John Caughman (Portland State U.)
Distance-regular graphs and spin models 29 Holly Swisher
The Andrews-Stanley partition function and p(n)
April
5 Jose Dias da Silva
TBA 12 Marcelo Aguiar (Texas AM)
Loday's types of algebras and Rota's types of operators 19 Brian Hartwig
Three mutually adjacent Leonard pairs 26 Christine Heitsch
Further combinatorial results motivated by computational biology
May
3 Darren Neubauer
Raising and lowering maps and modules for the quantum affine sl2 algebra 10 John Hall
Semigroups and combinatorics: radicals, Schur functions, and sandwich matrices

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Fall 2003 Schedule

     
September
8 Jim Propp
Markoff numbers 15 Yuval Roichman (Bar Ilan)
Descent representations and the flag major index 22 Sergey Fomin (U. Michigan)
Double Bruhat cells: total positivity and cluster algebras 29 Slavik Jablan (Belgrade)
The Knot-theory program LinKnot
October
6 Jaclyn Anderson
On the existence of rook equivalent t-cores 13 Mona Musa (U. Illinois)
The double circulant conjecture for quadratic residue codes 20 No meeting
27 Lev Borisov
Complexity of binomial ideals
November
3 Richard Brualdi
Bigraphs, digraphs, SNS-matrices, tilings, and Aztec diamonds 10 Peter Orlik
Ranking patterns 17 Ada Chan (Caltech)
Jones pairs and association schemes 24 Patricia Hersh (U. Michigan)
A GL_n(q) analog of the partition lattice
December
1 Matt Ondrus
Whittaker modules, central characters and tensor products of modules for U_q(sl_2) 8 Susan Hollingsworth
k-ordered bipartite graphs

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Spring 2003 Schedule

     
January
27 Christine Heitsch
Combinatorial results motivated by computational biology
February
3 Arun Ram
Diagram algebras 10 Jeremy Lovejoy
Overpartitions 17 Lev Borisov
Jacobi triple product formula and boson-fermion correspondence 24 Paul Terwilliger
Some tridiagonal pairs associated with quantum affine sl2.
March
3 Sylvie Corteel
Lecture hall theorems 10 Uri Keich (UCSD)
On designing seeds for similarity search in genomic DNA 24 Eric Mortenson
Supercongruences for truncated hypergeometric series 31 Richard Brualdi
List colorings of graphs and SDRs
April
7 Jackie Anderson
Does there exist a [72,36,16] type II code? 14 Brian Hartwig
Leonard pairs in the representation theory of Uq(sl2) 21 Darren Neubauer
Introduction to the q-shuffle algebra 28 Steve Kirkland (U. Regina Canada)
Digraph-based conditioning for Markov chains
May
5 Richard Askey
A new look at Fibonacci numbers

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Fall 2002 Schedule

     
September
9 Nigel Boston
The probability of generating a finite group 16 Aleksandar Jurisic (U. Ljubljana Slovenia)
Locally GQ tight distance-regular graphs 23 Arlene Pascasio (U. De La Salle Philippines)
On the multiplicities of the primitive idempotents of a distance-regular graph 30 Paul Terwilliger
Leonard pairs and orthogonal polynomials
October
7 Hjalmar Rosengren (Chalmers U. Tech. Sweden)
Leonard pairs and quantum group theory 14 Bogdan Petrenko (U. Illinois)
On the sum and the product of two primitive elements of maximal subfields of a finite field 21 Stephen Griffeth
Alternating sign matrices and the K-theory of flag varieties 28 Mourad Ismail (U. South Florida)
Rogers-Ramanujan identities and difference equations
November
4 Richard Brualdi
Matrices in combinatorics with applications 11 Jacob Christiansen (U. Copenhagen Denmark)
The log-normal moment problem 18 Brian Hartwig
Clusters of Leonard pairs 25 Georgia Benkart
Aztec diamonds and the (in)famous rho
December
2 Yang Chen (Imperial College UK)
Generalized Chebyshev Polynomials 9Timo Seppalainen
Increasing path models and interacting particle systems

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Spring 2002 Schedule

     
January
28 Yiftach Barnea
Hausdorff dimensions and the Nottingham group
February
4 Paul Terwilliger
Two linear transformations each tridiagonal with respect to an eigenbasis for the other: a canonical form 11 Morgen Bills (U. Michigan)
Brauer tableaux, Brauer polytabloids, and some sign-reversing involutions 18 Arun Ram
Generalizing the dominance order on partitions 25 Antal Balog
What is A if A+A is small?
March
4 Karl Mahlburg
Partition identities and a theorem of Zagier 11 Hiroshi Suzuki (Ohio State U.)
Type II matrices and their Bose-Mesner algebras 18 Richard Brualdi
Maximal nests of subspaces with an application to graph coloring 25 Spring break
April
1 Susan Hollingsworth
On a conjecture about trees in graphs with large girth 8 Patricia Hersh (U. Michigan)
Optimizing discrete Morse functions 12 Jonathan David Farley (U. Vanderbilt)
Differential posets and distributive lattices: a 1975 conjecture of Richard Stanley 15 Hans Schneider
The recent discovery of Wielandt's proof of the exponent inequality for primitive nonnegative matrices 22 Geir Helleloid
The m-step competition graph of a digraph 29 Kendra Nelsen
Charge and the Kostka-Foulkes polynomial
May
6 Georgia Benkart
Some Temperley-Lieb combinatorics

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Fall 2001 Schedule

     
September
10 Arun Ram
Introduction to affine Hecke algebras 17 Jack Koolen (Eindhoven)
The energy of a graph 24 Richard Brualdi
Linear preservers and diagonal hypergraphs
October
1 Bill Martin (Worcester Polytechnic)
The biweight enumerator and the subconstituent algebra of the hypercube 8 Gerald Cliff (U. Alberta)
Determining irreducible modular GL(n,K)-modules 15 Ken Ono
Questions and theorems about t-core partitions 22 Hans Schneider
Diagonal scaling: sunny side up and once over lightly 29 Brian Curtin (U. South Florida)
Graph Homomorphisms and Graph Automorphisms
November
5 Eric Bach (CS dept UW)
Combinatorial analysis of quantum random walks 12 Hiroshi Suzuki (Ohio State U.)
On weakly distance-regular digraphs 19 Matt Bloss
Irreducible representations of a centralizer algebra of a complex reflection group 26 Alexander Kleshchev
Representations of alternating groups and beyond
December
3 Jack Koolen
Are there finitely many distance-regular graphs with fixed valency? 10 Brian Hartwig
Truncated hypergeometric series

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Spring 2001 Schedule

     
January
22 Paul Terwilliger
How to recognize a Leonard pair 29 Mike Lang
Distance-regular graphs and the Q-polynomial property
February
5 Jim Propp
Domino Tilings: enumeration, random generation, and asymptotics 12 Warren Johnson
Combinatorics of higher derivatives of inverse functions 19 Alberto Elduque
Maximal subalgebras of associative superalgebras 26 Bryan Shader (U. Wyoming)
Dynamics, digraphs and diophantine equations
March
5 Matt Bloss
Centralizer algebras of complex reflection groups 12 Spring break
19 Susan Hollingsworth
TBA 26 Alexei Borodin (U. Penn)
Harmonic analysis on the infinite symmetric group
April
2 Arnold Neumaier (U. Vienna, Austria)
Large-scale mixed model estimation for animal breeding and census data 9 Richard Askey
Some elementary combinatorics related to teaching 16 Alexei Zhedanov (Donetsk Inst. of Physics, Ukraine)
Spectral transformations, numerical algorithms, self-similarity and special functions 23 Paul-Hermann Zieschang (U. Kiel)
Local and global scheme theory 30 Gwynneth Coogan
A combinatorial identity and an application to Hurwitz Zeta functions
May
7 Free

Combinatorics Seminar
Monday at 2:25pm
901 Van Vleck
Fall 2000 Schedule

     
September
11 Alexsandar Jurisic (Nova Gorica Polytechnic, Slovenia)
Distance-regular graphs with the 1-homogenous property 18 Paul Terwilliger
Leonard pairs from 24 points of view 25 Susan Hollingsworth
Partitions of a graph into paths with prescribed endvertices and lengths
October
2 Arun Ram
Standard Young tableaux for classical type root systems 9 Jeremy Lovejoy
Arithmetic properties of combinatorial functions 16 Chris Godsil (U. Waterloo, CA)
Spin Models 23 Bill Martin (Worcester Polytechnic)
Width and Dual Width of Subsets in P- and Q- polynomial schemes 30 Katsuhisa Mimachi (Kyushu U. Japan)
Monodromy representations associated with a Selberg type integral; realization of the Iwahori-Hecke algebra
November
6 Robert Donnelly (Murray State U.)
Solitary bases for representations of semisimple Lie algebras 13 Norman Wildberger
A-D-E graphs and the mutation and numbers games 20 Georgia Benkart
Tensor powers of sl(r) 27 Andrei Kelarev
On transitive Cayley graphs of groups and semigroups
December
4 Mark Maclean
Latin squares without proper subrectangles 11 John Caughman (Portland State U.)
Bipartite distance-regular graphs with the Q-polynomial property