Current students

Title: Stochastic Optimization

Abstract: While deterministic optimization problems are very useful in practice, often times the assumption that all data is known in advance does not hold true. One possible way to relax this assumption is to assume that the data depends on random variables. This assumption leads to stochastic optimization problems.

Title: Bounded treewidth in hereditary graph classes

Abstract: A highlight of the superb graph minors project of Robertson and Seymour is their so-called Grid Theorem: a minor-closed class of graphs has bounded treewidth if and only it does not contain all planar graphs. Which induced-subgraph-closed graph classes have bounded treewidth?

Title: 3-colouring via flows

Abstract: I'll show a technique to colour graphs on surfaces using max-flow min-cut.

Title: Determinantal formulas with major indices

Abstract: Krattenthaler and Thibon discovered a beautiful formula for the determinant of the matrix indexed by permutations whose entries are q^maj( u*v^{-1} ), where “maj” is the major index. Previous proofs of this identity have applied the theory of nonsymmetric functions or the representation theory of the Tits algebra to determine the eigenvalues of the matrix.

Title: A Brief Introduction to World of Erd\H{o}s-Ko-Rado Theorems

Abstract:   The Erd\H{o}s-Ko-Rado (EKR) theorem is a famous result that is one of the cornerstones of extremal set theory. This theorem answers the question "What is the largest family of intersecting sets, of a fixed size, from a base set?"

Title: On the Security of the NIST lightweight Finalist Ascon

Abstract: 

The ongoing NIST lightweight cryptographic standardization project for the selection of ciphers which are suitable for constrained environments is in the final stage. The authenticated encryption algorithm Ascon, designed by Dobrauing et al., is one out of the 10 finalists. Ascon is also one of the winners of the CAESAR competition in the lightweight applications category.

Title: An into introduction to the chromatic number of digraph

Abstract: A proper $k$-coloring of a digraph $D$ is a coloring of the vertices such that every color class is acyclic, and the dichromatic number of a digraph $D$ is the minimum number $k$ such that there is a proper $k$-coloring of $D$. Many questions about the chromatic number can be asked about the dichromatic number, but as one will quickly observe, unsuspected complications arise when dealing with digraphs.

Title: Erdős-Ko-Rado results for flags in spherical buildings

Abstract: Over the last few years, Erdős-Ko-Rado theorems have been found in many different geometrical contexts including for example sets of subspaces in projective or polar spaces. A recurring theme throughout these theorems is that one can find sharp upper bounds by applying the Delsarte-Hoffman coclique bound to a matrix belonging to the relevant association scheme.

Title: Maximal cliques in strongly regular graphs

Abstract: In this talk, I will introduce a cubic polynomial that can be associated to a strongly regular graph Γ. The roots of this polynomial give rise to upper and lower bounds for the size of a maximal clique in Γ. I will explain how we can use this cubic polynomial to rule out the existence of strongly regular graphs that correspond to an infinite family of otherwise feasible parameters. This talk is based on joint work with Jack Koolen and Jongyook Park.

Title: Theorems and Exchange Graph Algorithms concerning Paths, Cycles and Trees

Abstract: Carsten Thomassen and I proved that in any graph G, the number of cycles containing a specified edge as well as all the odd-degree vertices is odd if and only if G is eulerian. Where all vertices have even degree this is a theorem of Sunichi Toida and where all vertices have odd degree it is Andrew Thomason's generalization of Smith's Theorem.