2014-15 Colloquia

Tuesdays at 4:10 in
Carver 202 or as announced

 

For more information, contact
Songting Luo
Derrick Stolee
Steve Butler

 
 

Fall 2014

 

September 30 - Marcus Bishop (ISU): Quiver presentations of algebras associated with finite Coxeter groups
Poster

October 7 - Open

October 14 -Alexander Roiterschtein (ISU)

October 17 (Friday) - Lili Ju (U So Carolina) Joint with CAM

October 21 -Chao Zhu (UW-Milwaukee)

October 28 -Garret Alston (U Oklahoma)

November 4 - Open

November 11 -Chao Yang (LBNL)

 

 

 

Abstracts

September 30 - Marcus Bishop (ISU): Quiver presentations of algebras associated with finite Coxeter groups

We will discuss the methods used to calculate quiver presentations of three algebras associated to finite Coxeter groups, namely, the descent algebra, the Mantaci-Reutenauer algebra, and the zero-Hecke algebra. The talk will be appropriate for a general audience and will introduce quivers, Coxeter groups, and all of the algebras discussed.

September 16 - John Harding (New Mexico State): Quantum structures

Quantum structures is broad term for a wide range of areas. The common theme is the study of mathematical structures motivated by quantum mechanics. Such structures are studied both for their own interest, and for their application to quantum mechanics. They are frequently non-commutative or non-distributive versions of more classical objects.

In this talk I'll discuss some of my results in a number of different parts of quantum structures. This is a bit of a tour through several areas in the field, some quite old, others very current. We will cross a range of areas from operator algebras, to ordered structures and universal algebra, to category theory. Hopefully we provide a view of at least a portion of the topics of interest in this broad field.

Derrick Stolee: Automated discharging arguments for density problems in grids

Motivated by problems in wireless sensor networks, we consider minimizing the density of an identifying code in the hexagonal grid. An identifying code is a set of vertices where every vertex in the grid is uniquely identified by its adjacent code elements. While the minimum density of an identifying code is known for the square and triangular grids, there is still a gap between the upper and lower bounds for the hexagonal grid. Most lower bounds are found using discharging, which is a method to demonstrate the interaction between local structure and global averages.

Verifying a discharging proof is straightforward but usually very tedious. However, the creation of a discharging argument can be very mysterious. We will present a new computer-automated approach to not only verify discharging arguments, but also to generate them from scratch. A critical component to this method is solving a linear program that will assign value to the specified discharging rules, resulting in the best possible proof using those rules. Using this method, we find a new lower bound of 23/55 (approximately 0.4181818) on the density of an identifying code in the hexagonal grid, improving on the current-best human-created proofs.

Mridul Nandi (Indian Statistical Institute, Kolkata) Minimum number of multiplication to compute a Delta-universal function

Delta universal function is a family of (multivariate polynomial) function with small differential probability. It is an important combinatorial object which has application in many areas of computer science. Any multivariate polynomial can be computed by a sequence of multiplication and addition. As multiplications are usually costlier operations than addition, we study the lower bounds on the number of multiplication to compute a delta universal hash function. In this talk, we obtain a concrete form of the lower bound. We also discuss memory requirement of computing such functions and how to tweak an optimum construction to reduce the memory constraint.


Archived

August 26 - Mridul Nandi (Indian Statistical Institute, Kolkata) Minimum number of multiplication to compute a Delta-universal function
Poster

September 2 - Derrick Stolee: Automated discharging arguments for density problems in grids
Poster

September 16 - John Harding (New Mexico State): Quantum structures
Poster