Contact Info
Combinatorics & Optimization
University of Waterloo
Waterloo, Ontario
Canada N2L 3G1
Phone: 5198884567, ext 33038
PDF files require Adobe Acrobat Reader.
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Title: Conic lifts of convex sets
Title: Critical Points at Infinity for Hyperplanes of Directions
Speaker: Stephen Gillen Affiliation: University of Waterloo Location: MC 5501 or contact Eva Lee for Zoom linkAbstract: Analytic combinatorics in several variables (ACSV) analyzes the asymptotic growth of series coefficients of multivariate rational functions G/H in an exponent direction r. The polytorus of integration T that arises from the multivariate Cauchy Integral Formula is deformed away from the origin into cycles around critical points of a “height function" h on V = V(H).
Title: An fcoloring generalization of linear arboricity
Title: Distanceregular graphs with primitive automorphism groups
Title: Bargain hunting in a Coxeter group
Title: Matroids without cliques
Speaker: Peter Nelson Affiliation: University of Waterloo Location: MC 5501 or contact Eva Lee for Zoom linkAbstract: The class of graphs that omit some fixed complete graph as a minor is very wellstudied; in particular, the densest graphs in the class are known. The analogous question for matroids is just as wellmotivated, but seems harder to answer. I will discuss some recent progress in this area, which reduces a bound from doubly exponential to singly exponential. This is joint work with Sergey Norin and Fernanda Rivera Omana.
Title: Edge domination in incidence graphs
Title: Taking limits in Godiagrams
Title: Rectangle covers and bounding the extension complexity of the correlation polytope
Title: Steiner Cut Dominants
Speaker: Volker Kaibel Affiliation: Otto von Guericke University Magdeburg Location: MC 5501 or contact Eva Lee for Zoom linkAbstract: For a subset of terminals T of the nodes of a graph G a cut in G is called a TSteiner cut if it subdivides T into two nonempty sets. The Steiner cut dominant of G is the Minkowski sum of the convex hull of the incidence vectors of TSteiner cuts in G and the nonnegative orthant.
Title : A Closure Lemma for tough graphs and Hamiltonian degree conditions
Speaker: Cléophée Robin Institution: Wilfrid Laurier University Location: MC 5479Abstract: A graph G is hamiltonian if it exists a cycle in G containing all vertices of G exactly once. A graph G is ttough if, ,for all subsets of vertices S, the number of connected components in G − S is at most S / t.
Title: Quasisymmetric varieties, excedances, and bases for the TemperleyLieb algebra
Speaker: Lucas Gagnon Affiliation: York University Location: MC 6029 please contact Olya Mandelshtam for Zoom linkAbstract: This talk is about finding a quasisymmetric variety (QSV): a subset of permutations which (i) is a basis for the TemperleyLieb algebra TL_n(2), and (ii) has a vanishing ideal (as points in nspace) that behaves similarly to the ideal generated by quasisymmetric polynomials. While this problem is primarily motivated by classical (co)invariant theory and generalizations thereof, the course of our investigation uncovered a number of remarkable combinatorial properties related to our QSV, and I will survey these as well.
Title: Subgraph Polytopes and Independence Polytopes of Count Matroids
Speaker: David Aleman Affiliation: University of Waterloo Location: MC 6029Abstract: Given a graph G=(V,E), the subgraph polytope of G is defined as the convex hull of the characteristic vector of the pairs (S,F) such that S is a nonempty subset of vertices and F is a set of edges contained in the induced subgraph G[S].
Title: On the complexity of quantum partition functions
Speaker: David Gosset Affiliation: University of Waterloo Location: MC 5501 or contact Eva Lee for Zoom linkAbstract: Quantum complexity theory has been intertwined with the study of quantum manybody systems ever since Kitaev's insight that computing their ground energies is an intractable quantum constraint satisfaction problem that is complete for a quantum generalization of NP.
Title: Inverse eigenvalue problem of a graph
Speaker: Jephian C.H. Lin Affiliation: National Sun Yatsen University Location: Please contact Sabrina Lato for Zoom linkAbstract: We often encounter matrices whose pattern (zerononzero, or sign) is known while the precise value of each entry is not clear. Thus, a natural question is what we can say about the spectral property of matrices of a given pattern. When the matrix is real and symmetric, one may use a simple graph to describe its offdiagonal nonzero support.
Title: DistanceRegular and DistanceBiregular Graphs
Speaker: Sabrina Lato Affiliation: University of Waterloo Location: MCAbstract: For a given diameter d and valency k, what is the maximum number of vertices a kregular graph of diameter d can have, and what graphs meet that bound? Although there is a straightforward counting argument to bound the number of vertices using the structural information, the problem of characterizing the graphs that meet the bound turns out to be a problem in algebraic graph theory, and helps gives rise to the notion of distanceregular graphs.
Title: Arrangements of Pseudolines, Tropical Grassmannians, and Generalized Scattering Amplitudes
Speaker: Freddy Cachazo Affiliation: Perimeter Institute Room: MC 6029Abstract: For each arrangement of (pseudo)lines on the projective plane, it is possible to construct a differential form that captures its combinatorial structure. The forms have simple poles whenever triangles shrink to a point in the arrangement, and share the same residue when two arrangements are connected via a "triangle flip".
Combinatorics & Optimization
University of Waterloo
Waterloo, Ontario
Canada N2L 3G1
Phone: 5198884567, ext 33038
PDF files require Adobe Acrobat Reader.
The University of Waterloo acknowledges that much of our work takes place on the traditional territory of the Neutral, Anishinaabeg and Haudenosaunee peoples. Our main campus is situated on the Haldimand Tract, the land granted to the Six Nations that includes six miles on each side of the Grand River. Our active work toward reconciliation takes place across our campuses through research, learning, teaching, and community building, and is centralized within our Office of Indigenous Relations.