# Colloquia

## Yuri Dabaghian

Topological approach to modeling spatial cognition

Date: 2/1/2017

Time: 9:00AM-11:00AM

Place: 401 Engineering Science Building

All are welcome.

## Yu Hu

Relating the connectivity of neural networks to dynamics: the effect of motifs and connecting network models across scales

Date: 1/30/2017

Time: 5:00PM-7:00PM

Place: 301 Health Sciences Center Biomedical Research Building

All are welcome.

## Liu and Zhang

There will be two speakers for this event.

Professor Liu, Hubei University, will speak on "Some Conjectures on the Signless Laplacian Spectral Radius of Graphs".

Professor Zhang, Xia'Meng University, will speak on "The Surviving Rate of Graphs for Firefighter Problem"

Liu Abstract: Here

Zhang Abstract: Here

Date: 11/18/2016

Time: 3:30PM-5:30PM

Place: 315 Armstrong Hall

## Xiangqian Zhou

Induction for "4-connected" Matroids and Graphs

A matroid M is a pair (E,I) where E is a ﬁnite set, called the ground set of M, and I is a non-empty collection of subsets of E, called independent sets of M, such that (1) a subset of an independent set is independent; and (2) if I and J are independent sets with |I|

Abstract: Here

Date: 10/28/2016

Time: 3:30PM-4:30PM

Place: 315 Armstrong Hall

## Yue Zhao

Vizing's conjectures and related problems

In 1965, Vizing proposed three conjectures about edge chromatic critical graphs which are Vizing’s Planar Graph Conjecture, Vizing’s 2-Factor Conjecture and the conjecture about the size of edge chromatic critical graphs. In 1968, Vizing proposed the Independence Number Conjecture that is a weaker conjecture than his 2-factor conjecture. In this talk, we will focus on the above four conjectures and talk about the progress and some related problems.

Date: 10/27/2016

Time: 3:30PM-4:30PM

Place: 315 Armstrong Hall

## Sean Sather-Wagstaff

Finiteness Conditions in Algebra

Mathematical objects that satisfy finiteness conditions are frequently easier to work with than arbitrary objects. For instance, finite dimensional vector spaces are nicer in many ways than infinite dimensional ones. In this talk, I will discuss a variety of classical finiteness conditions in algebra and other areas: what they are and why they are useful. I will conclude with some new results answering a modified version of a question of Huneke about finiteness of associated primes in local cohomology.

This talk will be accessible to graduate students.

Date: 10/25/2016

Time: 4:00PM-5:00PM

Place: 315 Armstrong Hall

## Zhi-Hong Chen

Cycles of claw-free graphs and Catlin's reduction method

In the study of cycles of claw-free graphs,

Ryj\'{a}\u{c}ek developed a very nice closure concept: For a connected claw-free graph $H$, there is a $K_3$-free graph $G$ such that its closure $cl(H)=L(G)$ and for each cycle $C_0$ in $L(G)$, there exists a cycle $C$ in $H$ with $V(C_0)\subseteq V(C)$. A theorem by Harary and Nash-Williams shows that a line graph $L(G)$ has a Hamiltonian cycle if and only if $G$ has a dominating closed trail.

Thus, to find a cycle in a claw-free graph $H$ can be reduced to finding a closed trail in the preimage $G$ of the line graph of $L(G)$, where $L(G)=cl(H)$.

In this talk, I will discuss applications of Catlin's reduction method to the study of cycles in claw-free graphs and discuss new results and solutions of some conjectures on claw-free graphs that we obtained recently.

Date: 10/14/2016

Time: 3:45PM-4:45PM

Place: 315 Armstrong Hall

## Liang Hong

Credibility Theory without Tears

After a brief introduction of the actuarial science program at Robert Morris University, I will introduce the basic framework of Bayesian statistics and classical theory of credibility theory, a topic heavily tested on SOA's Exam C.

The last part of the talk will give the latest development in credibility theory; this work was done by my colleague (Dr. Ryan Martin, at North Carolina State University) and me, and our project was jointly sponsored by the Casualty Actuarial Society and Society of Actuaries through 2015 Individual Grant. The technical details are kept to a minimum. Therefore, the talk is accessible to anyone with a background in calculus-based probability theory, that is, the basic topics on Exam P.

Dr. Hong received his PhD in mathematics from Purdue University. He has received grants from the Casualty Actuarial Society (CAS), Society of Actuaries (SOA), and State Farm Insurance Company; and he has given research talks at several Center for Actuarial Excellence (CAE) schools including Drake University, Georgia State University, Temple University, University of Waterloo, University of Wisconsin, Madison.

Date: 9/23/2016

Time: 12:30PM-1:20PM

Place: 121 Armstrong Hall

## Hao Li

On the g-extra connectivity of $3$-ary $n$-cube networks

Let $G$ be a connected graph and let $F$ be a set of vertices.

The $g$-extra connectivity of $G$ is the cardinality of a minimum set

$F$ such that $G-F$ is disconnected and each component of $G-F$ has at

least $g+1$ vertices. The $g$-extra connectivity is an important

parameter to measure the reliability and fault tolerance ability of

large interconnection network of parallel computing systems.

In 2011, the $g$-extra connectiviy for $g=1,2$ of 3-ary $n$-cubes are

gotten by Zhu et al. The 3-extra connectivity of 3-ary $n$-cubes are

given by Gu and Hao in 2014. Here, we determine the $g$-extra

connectivity of 3-ary $n$-cubes for $0\le g \le 2n$.

Date: 8/25/2016

Time: 3:45PM-4:45PM

Place: 315 Armstrong Hall

## Xiao-Dong Zhang

Some Extremal Graph Results with Degree Sequences

As it is said in the book \Extremal Graph Theory" by Bollobas, in extremal graph theory one is interested in the relations between the various graph variants, such as order, size, connectivity, minimum degree, maximum degree, chromatic number and diameter, and also in the values of these in-variants which ensure that the graph has certain properties. In this talk, we introduce some progresses and results on graph variants, such as spectral radius, Laplacian spectral radius, the average distance, and the number of sub-trees for a class of graphs with given degree sequences, and we also introduce some related open problems.

Professor Xiao-Dong Zhang's Website

Date: 8/23/2016

Time: 3:30PM-4:30PM

Place: 315 Armstrong Hall

## Pages