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Past Combinatorics and Algebra Seminars Fall 2023 September 22~ Recent Developments s in the Fundamental Theorem of Algebra Mohsen Aliabadi September 29 (virtual, on zoom)~ On the Partition Regularity of ax + by = cw^mzⁿ Sohail Farhangi October 13~ When is the group of units as additively closed as possible? Neil Epstein The doc cam notes from the talk October 20~ How to show that a ring has uncountable krull dimension Jack J. Garzella October 27~ Title: Combinatorial Aspects of the Alternating Sign Matrix Elizabeth A. Dinkelman December 1, 11 am -- 12 noon NB! Unusual time! (virtual, on zoom)~ Real-time Formalization of Mathematics Kevin Buzzard Spring 2023 February 3 (in person and zoom)~ Egyptian integral domains Neil Epstein The doc cam notes from the talk March 3 (in person and zoom)~ Helly-type theorems on support lines for convex bodies in the plane Valeriu Soltan March 24 (virtual zoom)~ Generalized Turán problems and a new localized approach Rachel Kirsch April 7 (virtual zoom)~ Coloring Reconfiguration Reem Mahmoud April 14 (in person and zoom)~ A semigroup presentation for the singular part of the partial endomorphism monoid of a free G-act (of finite rank) Scott Carson April 28 (in person and zoom)~ Multiplier ideals and klt singularities via (derived) splittings Peter Morton McDonald May 3, 11am -- 12 noon (in person and zoom Note! Unusual time)~ Perfectoid signature and an application to étale fundamental groups Karl Schwede Fall 2022 October 28 (in person and zoom)~ Global perinormality in a generalization of a `D + M` construction and graded perinormality Hannah Klawa November 4 (in person and zoom)~ Infinitude Results for Prime Polynomials Brian L. Johnson November 11 (in person and zoom Talk postponed until further notice)~ Perfectoid signature and an application to étale fundamental groups Karl Schwede November 16 (virtual on zoom, NB! Unusual time: Wednesday 12:30 -- 1:30 PM EST)~ Parity property of hexagonal sliding puzzles Érika Roldán November 18 (virtual on zoom)~ Local Brooks’ Theorems Magnús Már Halldórsson December 2 (in person and zoom, NB! An hour later than usual: 1:30 -- 2:30 PM EST )~ Distractions and Generic Initial Ideals Anna-Rose Wolff Spring 2022 February 25 (virtual)~ Canonical forms of neural ideals Rebecca R.G. March 11 (in person and zoom)~ Boundedly polyhedral sets and F-simplices Valeriu Soltan March 25 (in person and zoom)~ Promotion, rotation, and a web basis of invariant polynomials from noncrossing partitions Jessica Striker April 1 (in person and zoom)~ Arithmetic dynamics on character varieties Cigole Thomas April 8 (in person and zoom)~ What makes a diagram commute? Richard H. Hammack April 22 (virtual)~ Parity property of hexagonal sliding puzzles Érika Roldán Fall 2021 October 8 (virtual)~ Groups, lattices, and closure operators Arturo Magidin October 15 (virtual)~ Permutation statistics and moment sequences Einar Steingrímsson October 29 (virtual)~ Higher dimensional origami constructions Adriana Salerno November 5 (virtual)~ Universal partial cycles Rachel Kirsch November 12~ Hurwitz action in complex reflection groups Jiayuan Wang December 3 (virtual)~ Deep neural networks and DNA variant effect predictions in humans Ágúst Egilsson Spring 2021 February 26~ Ideals of skew-symmetric matrix Schubert varieties Brendan Pawlowski March 12~ Whitney duals and Whitney twins: a plausible approach to questions related to Whitney numbers Rafael S. González Di León March 19~ Sum-product and convexity Brandon Hanson April 9~ Probabilistic generalizations of the Robinson– Schensted correspondence Gabriel Frieden NB! A talk of possible interest to the CAGS community: (virtual, see flyer for the Zoom link) Tuesday, April 13, 12 – 1 pm~ New approaches to quantum matter from hyperbolic geometry Steven Rayan April 16~ NB! An hour delay (now at 1:30 pm) Steiner configurations ideals: containment and colorability Abu Chackalamannil Thomas April 23~ Data Science – Requirements and Applications Colton Magnant Fall 2020 September 18~ Dedekind, Prüfer, Krull, and factorial rings with or without zerodivisors Jesse Elliott September 25~ The free cone and its relation to matroid invariants Kevin Long October 2~ Three short proofs related to independence number and Lovasz' theta Craig E. Larson October 16~ From Efron's coins to alternation acyclic tournaments Gabor Hetyei October 23~ Minimal free resolutions of fiber products Hugh R.~Geller October 30~ Separating hyperplanes of convex sets Valeru Soltan November 20~ Limits of polygon spaces Jack Love Spring 2020 January 31~ ECH capacities, Ehrhart theory, and toric varieties Ben Wormleighton February 7~ Connected sums of Gorenstein Artin rings Ela Celikbas February 21~ Tiling, Terry Tao, Group Characters, and Fugledes Conjecture Sam Ferguson March 20~ TBA Postponed until further notice! Jack Love March 27~ TBA Postponed until further notice! Jesse Elliott April 24~ Independent sets, Lovasz’ theta, and linear programming Postponed until further notice! Craig E. Larson May 1~ TBA Postponed until further notice! Kevin Long Fall 2019 September 13~ A few problems on matrix rings Geir Agnarsson September 20~ Magic type labelings of cycle products Dalibor Froncek September 27~ Generalized Rings Carl Weisman October 18~ Involutions and pseudo-involutions in the Riordan group Alexander Burstein November 1~ The ring of differential operators in a generalized Stanley-Reisner ring Janet Vassilev November 15~ M-decomposable convex sets Valeriu Soltan November 22~ Trace modules over commutative rings Haydee Lindo December 6~ The dynamics of Boolean networks Reinhard Laubenbacher Spring 2019 February 1~ Vertex colorings of acyclic digraphs, efficiencies and discrepancies Geir Agnarsson March 1~ Lech’s inequality and the Stuckrad-Vogel conjecture Patricia Klein March 29~ Counting factorizations in complex reflection groups Joel Brewster Lewis April 5~ On the number of discrete chains Eyvindur Ari Pállson April 12~ Minimal generating sets for coordinate rings of representations Sean Lawton April 19~ Circular coloring of planar graphs Dan Cranston May 3~ No CAGS talk (MEGL poster session, hallway right outside EXPL 4106) GMU mathematics students. Fall 2018 September 7~ A proof of the strict monotone 5-step conjecture Walter Morris September 14~ Pseudoalgebras Carl Weisman October 5~ Moreau-Type Characterizations of Polar Cones Valeriu Soltan October 19~ Positivity in the S¹-equivariant cohomology of type `A` Peterson varieties Brent Gorbutt October 23~Tuesday\ 11 am -- 12 noon, ROOM 3301 EXPL. HALL. Polymatroids and excluded minors Carolyn Chun November 2~ Nearly Platonic graphs Dalibor Froncek November 9~ Helly-type results on support lines for disjoint families of unit disks Valeriu Soltan November 30~ The role of big Cohen-Macaulay modules and algebras in commutative algebra Rebecca R.G. Spring 2018 February 2~ Interval posets, parity representations, binary partitions, and antiprisms (Part I: 12:30 -- 1:00 pm) Jim Lawrence February 9~ Interval posets, parity representations, binary partitions, and antiprisms (Part II) Jim Lawrence February 23~ Colored subgraphs whose forbiddance implies monochromatic connectivity Colton Magnant March 2~ When does the content map on polynomials act like a homomorphism, and how broadly does the answer apply? (Postponed until March 9) Neil Epstein March 30~ Hamiltonian cycles in critical graphs with large maximum degree Yue Zhao April 6~ Routing numbers of some graphs Gexin Yu April 13~ The Set-Maxima problem Indranil Banerjee April 27~ Diffuse Interfaces and Topology: A Phase-Field Model for Willmore’s Energy (Special Applied Math and CAGS Joint Seminar) Stephan Wojtowytsch May 4~ Applications of ordinary voltage graph theory and intersection theory to graph embeddability, (and some notes about toplogical data analysis) (NB! 11:30 am, due to Math Dept luncheon) Steven Schluchter Fall 2017 September 8~ Sequential Importance Sampling Algorithms for Estimating Tree Size Alathea Jensen September 15~ Extremal finite subgraphs of the grid graph Geir Agnarsson. October 6~ Permutation Routing Via Matchings Indranil Banerjee. October 20~ SIAM Faculty Seminar October 27~ Separation and polarity properties of convex cones Valeriu Soltan. November 3~ Algebraic and combinatorial interpretations of tight closure theory on Stanley-Reisner rings Thomas Ales. November 10~ Unbalanced Wilf-equivalence Alexander Burstein. December 1~ TBA postponed! Jacob Farinholt December 8~ Symbolic powers and differential operators Eloísa Grifo Spring 2017 February 10~ Generalized depth in the perfect closure George E. Whelan February 24~ Acyclic digraphs giving rise to complete intersections Walter Morris March 3~ How well-behaved is your ring map? The Ohm-Rush content function reconsidered Neil Epstein March 24~ Distance magic and group distance magic graphs Dalibor Froncek April 21~ Edge-coloring of graphs and multigraphs Dan Cranston April 28~ Conjugation of Transitive Permutation Pairs and Dessins d'Enfants Sean J. Rostami May 5~ Hessenberg varieties and the Shareshian-Wachs conjecture Patrick Brosnan Fall 2016 September 9~ Doubly weighted rooted trees and computer security systems Geir Agnarsson October 7~ Self-polar polytopes Alathea Jensen October 14~ A great tool from the polynomial method toolkit: the Alon-Füredi Theorem John R. Schmitt October 27~ NB! Thursday at 12 noon Decompositions of complete bipartite graphs into generalized prisms Dalibor Froncek October 28~ A new perspective on the G-Invariant of a matroid Joseph E. Bonin November 4~ Khovanskii bases, Newton-Okounkov polytopes, and tropical geometry of projective varieties Chris Manon November 18~ Minimal ring extensions Jay Shapiro Spring 2016 February 12~ Max-weight rooted-subtree problem and computer security Geir Agnarsson March 4~ A directed Steinitz theorem for oriented matroid programming Walter Morris March 18~ Characteristic properties of ellipses Valeriu Soltan March 25~ The Diophantine Frobenius Problem: Past, Present and Future Elie Alhajjar April 1~ Even the Patriots can win Atlantic 10! Dalibor Froncek April 5~NB! Tuesday at 12:30! On the Maximum Genus of Planar Graphs Lara Sherif April 8~ Matrix rings and representations Sam Mendelson April 22~ Geometry of Peterson Varieties in Lie Type A Brent Gorbutt April 29~NB! At 12 noon! In pursuit of canonical structures on cellularly embedded graphs Jason Suagee Fall 2015 September 18~ Differential graded manifolds as a model for derived manifolds David Carchedi October 2~ On a special class of general permutahedra Geir Agnarsson October 16~ Negatively Self-Polar Polytopes Alathea Jensen October 30~ LP Alchemy for the Stability Number of a Graph Craig Larson November 6~ Prime congruences and Krull dimension for additively idempotent semirings Kalina Mincheva November 13~ On the Geometry of Quantum Weak Measurements Jacob Farinholt December 4~ Self-dual embeddings of `K_{4m,4n}` in orientable and nonorientable pseudosurfaces with the same Euler characteristic Steven Schluchter Spring 2015 February 13~ Various generating functions, a unifying approach Geir Agnarsson February 20~ The Dedekind-Mertens Theorem for power series and more generally arbitrary algebras over `R` Jay Shapiro February 27~ The Zariski topology on sets of semistar operations Dario Spirito March 6~ Algebraic measures of singularity Javid Validashti March 20~ Graph Theory Tools for Tournament Scheduling Dalibor Froncek March 27~ Mihalisin - Klee Theorem for Fans Rachel Locke April 3~ Digital Geometry: New Trends and Developments Li Chen April 10~ The Complementarity Polytope, Pauli operators, and the Clifford Group Jacob Farinholt April 17~ Prime labelings of generalized Petersen graphs Kathryn Cokus, Ryan Ellingson, and Thomas Wilson (co Justin Z. Schroeder and Steven Schluchter) April 24~ The Survival Complex Anna-Rose Wolff May 1~NB! at 12 noon Homological algebra of graphs Arindam Banerjee Fall 2014 August 29~ Parking functions & friends Matthias Beck September 5~ Applications of ordinary voltage graph theory to graph embeddability, part I Steve Schluchter September 19~ Base-Orderability in Matroids Thomas Savitsky October 17~ The Traveling Salesman Problem and P vs. NP: Some 1960s Theoretical Work at NIST On the Complexity of Mathematical Algorithms Jack Edmonds October 24~ Poincare-Bett Series of Monomial Rings Gwyneth Whieldon October 31~ Valuations on Convex Sets Jim Lawrence November 7~ Puzzles and (many flavors of) Schubert calculus Allen Knutson November 14~ Applications of ordinary voltage graph theory to graph embeddability, part II Steve Schluchter Decemver 5~ Some special matrix algebra presentations Samuel Mendelson Spring 2014 January 31~ Induced subgraphs of hypercubes Geir Agnarsson February 21~ Mutually Unbiased Bases Jacob Farinholt February 28~ Ring extensions involving amalgamated duplications Tim Long March 28~ Triangle inequalities in representation theory and algebraic geometry Chris Manon April 4~ Ring extensions invariant under group action: flat epimorphic extensions Amy Schmidt April 11~ Test Ideals of Non-principal Ideals Karl Schwede April 18~ Threshold Digraphs James Shook May 2~at 12 noon! Strong Krull primes and flat modules Neil Epstein Fall 2013 September 6~ Informal discussion on Gelfand-Tsetlin Polytopes (ongoing) Rebecca Goldin and Chris Manon September 13~ Informal discussion on Gelfand-Tsetlin Polytopes (ongoing) Rebecca Goldin and Chris Manon September 20~ Some naturally occurring matroids and matroid-like structures in commutative algebra Neil Epstein September 27~ A survey on graphs with a distinguishing partition Justin Z. Schroeder October 4~ Complete Intersection Affine Semigroup Rings Arising from Posets Walter Morris October 11~ Informal discussion on Gelfand-Tsetlin Polytopes (ongoing) Rebecca Goldin and Chris Manon October 18~ Informal discussion on Gelfand-Tsetlin Polytopes (ongoing) Rebecca Goldin and Chris Manon October 25~ Ordinary voltage graphs, pseudosurfaces, and derived graph embeddings with applications to graph embeddability Steven Schluchter November 8~ Hom polytopes between regular polytopes Jack Love November 22~at 11:30am The geometry of the quotient stack arising from a stacky fan David Johannsen Spring 2013 February 1~ Schubert Calculus of Weighted Grassmannians Tomoo Matsumura February 8~ Zero-divisor graphs of nilpotent-free semigroups Neil Epstein February 15~ Coloring claw-free graphs with `Δ-1` colors Dan Cranston March 1~ Zero-divisor graphs of nilpotent-free semigroups, part II Neil Epstein March 22~ "Graph" Saturation Michael Jacobson March 29~ Properties of the Copoint Graph of Convex Geometries Jonathan Beagley April 12~ Some basic properties of primary decomposition Yongwei Yao April 19~ Dimension and Height for Posets with Planar Cover Graphs Noah Streib April 26~ Approximating the Partition Function of the Ising Model Amanda Streib May 3~ Hyperbolic surfaces, circle maps and geometry of Teichmuller spaces Dragomir Saric Fall 2012 September 7~ Clique Number and Chromatic Number of Graphs defined by Convex Geometries Walter Morris September 14~ Algebra and geometry of archimedean integers in general number fields Carl Weisman September 28~ Going-down in monoid rings Jay Shapiro October 5~ Turning conformal field theory into combinatorics Chris Manon October 12~ A Happy Coloring Theorem Jonathan Beagley October 19~ Pebbling in Split Graphs Glenn Hurlbert November 2~ Multi-Sources Simultaneous Communication in the Wireless Mobility Model is NP-complete Pattama Longani November 16~ Some problems in ring theory Geir Agnarsson Spring 2012 February 3~ Schröder paths, partial horozontal strips, and symmetric functions Sangwook Kim March 2~ Davis matrics of sections and projections of polyhedral cones Jim Lawrence March 9~ On a Carathéodory theorem for Minkowski sum of polytopes Geir Agnarsson March 23~ Recent advances in biclique decompositions Walter Morris April 6~ On edge chromatic critical graphs Yue Zhao April 13~ Categorifications of the chromatic polynomial Radmila Sazdanovic April 20~ Carathéodory-type results for the sums and unions of convex sets Valeriu Soltan NB! Postponed until further notice. May 4~ Patterns in permutations Alexander Burstein Fall 2011 September 9~ Induced subgraphs of Z2 and related extremal graphs Geir Agnarsson September 16~ An abstract structure theorem for suborder lower ideals of series-parallel posets Christian J. Altomare September 23~ Hamilton Bond, Tutte Bond and Tutte Theorem Xiaoyun Lu October 7~ Global Weyl modules for twisted loop algebras Prasad Senesi October 21~ Tropical geometry of flag varieties and the space of phylogenetic trees Chris Manon October 28~ Art Galleries, Fortresses, and Prison Yards: Illumination and Color T. S. Michael November 4~ An Introduction to Simplicial Geometries Cynthia S Merrick November 11~ The Order Dimension of Convex Geometries Jonathan Beagley November 18~ Applying the stuff we like: blocking semiovals and cryptology Keith Mellinger Spring 2011 February 4~ The incidence algebra of a poset and enumerations Geir Agnarsson Febrary 18~ The type A Coxeter complex in algebraic combinatorics Forest Fisher Febrary 25~ A Projective approach to auantum error correcting codes Jacob Farinholt March 9, 12 noon -- 12:50 pm Unifying Laver's theorem and the Graph Minor Theorem via proof system minors Christian Altomare Note! This talk is on a WEDNESDAY at noon! March 11~ Convex quadrics Valeriu Soltan April 15~ A Projective approach to auantum error correcting codes, 2nd part Jacob Farinholt April 22~ Polytopes from graphs Jim Lawrence April 29~ Spies and revolutionaries Dan Cranston Fall 2010 September 10~ Oriented Matroids and N-step Vectors Walter Morris September 17~ Combinatorial identities for subspaces and finite sets Geir Agnarsson October 8~ Combinatorial Hopf algebras by way of groups Forest Fisher, GWU October 22~ Some Interesting Classes of Convex Polytopes Jim Lawrence November 12~ An Attempt to Turn Geometry into Decorated Graphs Rebecca Goldin November 19~ Homology of distributive systems: a historical perspective Jozef Przytycki, GWU December 3~ Points, Copoints, and Colorings Jonathan Beagley December 10~ New Results on Graph-Theoretic Independence Craig Larson, VCU Spring 2010 January 29~ The hitting time subgroup, Lukasiewicz paths, and Faber polynomials Gi-Sang Cheon, SungKyunKwan University S&T I room 242 February 19~ Some graph labellings, complexities and connections to groups Geir Agnarsson S&T I room 206 March 5~ Generalized rings: examples and applications Carl Weisman S&T I room 206 March 19~ Workshop on Combinatorics, Enumeration, and Invariant Theory (WCEIT) S&T I room 242 March 26~ Holes in a polytope defined by degree sequences Walter Morris S&T I room 206 April 2~ On intersections and composites of minimal ring extensions Jay Shapiro S&T I room 206 April 9~ Leavitt Path Algebras Gene Abrams, University of Colorado at Colorado Springs S&T I room 206 April 23~ Ordered trees, the uplift principle and the Riordan group Lou Shapiro, Howard University S&T I room 206 Fall 2009 September 18~ Survey of recent papers on the Hirsch conjecture Walter Morris September 25~ Making K-theory combinatorial Rebecca Goldin October 2~ Betti numbers of graphs David Johannsen October 16~ f- and h-vectors for complexes, polytopes and beyond Geir Agnarsson October 23~ How Five Regular Solids Turned into Seventy-five Steve Morse October 30~ Helly-Type Results on Common Supports of Convex Bodies Valeriu Soltan December 4~ Topology of real coordinate arrangements Sangwook Kim Spring 2009 January 30~ Mixed dominating matrices Walter Morris February 16 (Monday at 2:30 in S&T I, room 220)~ The Graham-Pollak Theorem and Alon-Saks-Seymour Conjecture Reza Naserasr, Carleton University February 27~ Embedding Quadratic Number Fields in Cyclotomic Fields Bill Ellis March 6~ Bruhat order and hyperplane arrangements Sangwook Kim March 20~ Thin Partially Ordered Sets Mikhail Matveev April 3~ The Geometry of Kissing: Soddy Circles, Apollonian Gaskets, and a Problem in Geometric Graph Theory Jill Dunham April 10~ On the flag polynomial of Minkowski sum of standard simplices Geir Agnarsson Fall 2008 September 12~ Szekeres and Peters' computer proof of the 17-point Erdos-Szekeres problem Walter Morris September 19~ On the structure of the Minkowski sum of standard simplices Geir Agnarsson September 26~ On the structure of the Minkowski sum of standard simplices, Part II Geir Agnarsson October 3~ The lattice of cyclic flats of a matroid Joseph Bonin October 17~ On Minkowski rings Jim Lawrence October 24~ On the openness of the contraction map to the fixed ring Jay Shapiro October 31~ The free splice of matroids William Schmitt November 7~ Rational Representations of Flowers Jill Bigley Dunham November 14, 1:30 - 2:30 (NB! the time of the Applied and Computational Math Seminar)~ Random Threshold Graphs Edward Scheinerman November 21~ An Introduction to Lie Algebras and their Cohomology Robert F. Allen Spring 2008 January 30~ (no talk) February 6~ (no talk) February 13~ The importance of fixed point\s in group actions on symplectic manifolds Rebecca Goldin February 20~ On rational distances between \points on a quadratic curve in the Euclidean plane Steven D. Lepiere February 27~ Some Combinatorial Types of Polyt\opes Jim Lawrence March 5~ Universal lying-over rings Jay Shapiro March 26~ Graph labeling, complexity and vari\ants Geir Agnarsson April 2~ Graph labeling, complexity and varia\nts (2nd part, but self-contained!) Geir Agnarsson Friday April 4, 11:30 - 12:30, Room 242 (NB! time and place)~ Horse racing, card games, theorems in matrix theory, and consequences Chi-Kwong Li April 9~ Simple vertices in a Minkowski sum\s of simplices Walter Morris April 16~ (no talk) April 23~ (no talk) April 30~ The Cantor Tree and things that a\re like it Ronnie Levy Fall 2007 Sept. 14~ Flag enumeration of matroid base poly\topes Sangwook Kim Sept. 21~ (no talk) Sept. 28~ Shellable complexes and topology of \diagonal arrangements Sangwook Kim Oct. 5~ Quadrilateral embedding of $G \times Q_s$\ Paul C. Kainen Oct. 19~ Shellable complexes and topology of d\iagonal arrangements, part II Sangwook Kim Oct. 26~ Intordcutoin to Rnadom Garphs Nate Shank Nov. 9~ Graph theoretic proof of the Amitsur-Levits\ki theorem Geir Agnarsson Nov. 30~ We recommend the CDS/CCDS/Statistics Colloquium talk: Social Networks via Random Dot Product Graphs David Marchette Spring 2007 Feb. 23~ Vertex coloring acyclic digraphs Geir Agnarsson Mar. 2~ Vertex coloring acyclic digraphs (Second Part) Geir Agnarsson Mar. 9~ (no talk) Mar. 16~ (Spring Break) Mar. 23~ An introduction to PPAD search problems Walter Morris Mar. 30~ (no talk, faculty meeting at 3:30) Aprli 6~ (no talk) April 13~ A quasisymmetric function for matroids Louis J. Billera NB! This is the first of two talks by Billera. The second talk will be later the same day at our departmental Colloquium. April 20~ Simple Arrangements of Pseudolines, and their Other Lives Jim Lawrence Aprli 27~ (no talk) May 4~ The Euler characteristic and Euler's formula for convex polytopes (with proofs) Jim Lawrence Fall 2006 Sept. 15~ On Coin Graphs and Other Contact Graphs Geir Agnarsson Sept. 22~ Collineations and affine transformations in Euclidean space Valeriu Soltan Oct. 13~ Minkowski sums of simplices Walter Morris Oct. 20~ An algorithmic game related to Schubert calculus Rebecca Goldin Oct. 27~ Limits to Parallel Computation: P-Completeness Theory Ray Greenlaw, Armstrong Atlantic State University and Fulbright Scholar at Chiang Mai University Tuesday, Oct. 31, 12:15-1:05~ Physical Supersymmetry for Mathematicians Greg Landweber, University of Oregon Nov. 17~ Good Hidden P-matrix Sandwiches Walter Morris Spring 2006 Feb. 10~ Sunflowers, Kneser Graphs and Intersecting Families Geoff McKenna, George Washington University Feb. 17~ No talk. We recommend the department colloquium at 3:30. Feb. 24~ On the empty hexagon theorem Walter Morris Mar. 3~ Gale transforms Jim Lawrence Mar. 10~ More Gale Transforms: K_5 in R^3 (or S^3) Jim Lawrence Mar. 24~ No seminar. The Math Club is arranging a talk at 1:15, on the Mathematics of Juggling, by Allen Knutson, UCSD. Mar. 31~ The transfer of Krull dimension in fixed rings Jay Shapiro April 7~ Invariants of n-tuples of points on the Riemann sphere under linear fractional transformations Ben Howard, UMCP April 14~ On finite groups Edith Adan-Bante, U. of Southern Mississippi Gulf Coast May 4~ 3PM The plus, minus game Klaus Fischer Fall 2005 Sept. 8 ~ Graphical condensation and its connection to plane partitions and MacMahon's formula Eric Kuo Sept. 15 ~ A classification of the minimal ring extensions of an integral domain Jay Shapiro Sept. 22 ~ Combinatorics of Viterbi Sequences Eric Kuo Sept. 29 ~ The simple stochastic game Walter Morris Oct. 6 ~ Extension of vertex maps to graph homomorphisms Geir Agnarsson Oct. 13 ~ Extension of vertex maps to graph homomorphisms, part II Geir Agnarsson Oct. 20 ~ No talk Oct. 27 ~ Discrete polymatroids Walter Morris Nov. 3 ~ No talkNov. 10 ~ No talk Nov. 17 ~ Case Studies in Shape and Trajectory Optimization: Catenary Problem Igor Griva Dec. 1 ~ TBA Jim Lawrence Spring 2005 Feb. 18 ~ Isothetic Parallelotopes and the Binary Intersection Property Valeriu Soltan Mar. 4 ~ Cluttered orderings for the complete bipartite graph and the complete tripartite graph Tomoko Adachi, Toho University, Japan Mar. 11 ~ Positive bases in Euclidean space Valeriu Soltan Mar. 25 ~ On multipartite posets Geir Agnarsson On multipartite posets Apr. 1 ~ Algebra and graph reconstruction Geoff McKenna, George Washington University Apr. 8 ~ NO TALK - we recommend the Math colloquium Apr. 22 ~ Good hidden P-matrix sandwiches Makoto Namiki, Toho University and George Mason University Apr. 29 ~ Good hidden P-matrix sandwiches, part II Makoto Namiki, Toho University and George Mason University

Past Combinatorics and Algebra Seminars