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Title: Maximizing nonmonotone submodular functions
Speaker: Zishen Qu Affiliation: University of Waterloo Room: MC 5417Abstract:
Optimization of nonmonotone submodular functions has applications in the maximum cut and maximum directed cut problems for graphs.
Title: A Quantum Query Complexity Trichotomy for Regular Languages
Speaker: Luke Schaeffer Affiliation: University of Waterloo Room: MC 5501Abstract:
We consider the quantum query complexity of regular languages and discover a surprising trichotomy: each regular language has query complexity either Theta(1), ~Theta(sqrt(n)) or Theta(n).
Title: Cospectral and strongly cospectral vertices
Speaker: Chris Godsil Affiliation: University of Waterloo Room: MC 5479Abstract:
If $a$ is a vertex in a graph with adjacency matrix $A$, the \textsl{walk module} generated by $a$ is the $A$invariant subspace spanned by the vectors $A^re_a$, for $r\ge0$.
Title: Twocolouring hypersurface complements in open Richardson varities
Speaker: Kevin Purbhoo Affiliation: University of Waterloo Room: MC 5417Abstract:
Given an algebraic hypersurface $H \subset \mathbb{R}^n$, we can always 2colour the components of the complement $\mathbb{R}^n \setminus H$ such that adjacent components are of opposite colours.
Title: Counting Pentagons in Trianglefree Binary Matroids
Speaker: Adam Brown Affiliation: University of Waterloo Room: MC 5501Abstract:
Every trianglefree graph with n vertices contains at most (n/5)^5 cycles of length five, and this value is attained by the balanced blowup of the 5cycle.
Title: Circuithyperplane relaxation and matroid representation
Speaker: Jim Geelen Affiliation: University of Waterloo Room: MC 5501Abstract:
Relaxing a circuithyperplane in a representable matroid can destroy representability.
Title: From weakly separated collections to matroid subdivisions
Speaker: Nick Early Affiliation: Perimeter Institute for Theoretical Physics Room: MC 5417Abstract:
We study arrangements of slightly skewed tropical hyperplanes, called blades, on the vertices of a hypersimplex $\Delta_{k,n}$.
Title: Halfway to Rota's Basis Conjecture
Speaker: Shayla Redlin Affiliation: University of Waterloo Room: MC 5501Abstract:
Rota’s Basis Conjecture is that any rankn matroid with n disjoint bases B_1, …, B_n has n disjoint transversal bases; a basis is transversal if it contains exactly one element from each B_i.
Title: A deterministic (1/2 + epsilon)approximation for submodular maximizztion over a matroid
Speaker: Ben Moore Affiliation: University of Waterloo Room: MC 5417Abstract:
In 1978, it was shown that a natural greedy algorithm gives a 1/2 approximation to submodular maximization subject to a matroid constraint.
Title: The combinatorics of parametric Feynman integrals
Speaker: Marcel Golz Affiliation: University of Waterloo Room: MC 5501Abstract:
Feynman integrals are used in perturbative quantum field theory to compute the probabilities of processes involving elementary particles. They can be represented as Feynman graphs and exhibit a rich combinatorial structure. The parametric representation of Feynman integrals is particularly suitable to be studied from a combinatorial perspective since it contains well known objects like the Kirchhoff polynomial.
Title: Kummer's Theorem on binomial coefficients, etc.
Speaker: John Schanck Affiliation: University of Waterloo Room: MC 5501Abstract:
Some of us like the primes and call ourselves pure mathematicians. Some of us like the Catalan numbers and call ourselves combinatorialists.
Title: Submodular function maximization via the multilinear relaxation and contention resolution schemes
Speaker: Sharat Ibrahimpur Affiliation: University of Waterloo Room: MC 5417Abstract:
I will present a general framework for maximizing a nonnegative submodular set function $f$ subject to a variety of packing type constraints including multiple matroid constraints, knapsack constraints, and their intersections.
Title: Disjunctive Cuts through the VPolyhedral Lens
Speaker: Aleksandr Kazachkov Affiliation: Polytechnique Montréal Room: MC 5501Abstract:
Cutting planes, or cuts, are a critical component of modern integer programming solvers, but existing cuts implemented in solvers are relatively simple compared to those in the literature. We discuss the primary reasons for this disparity, as well as our recentlyproposed Vpolyhedral framework for mitigating some of these difficulties encountered by prior "stronger" cuts.
Please email any errors or updates to our website support/editor.
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