COMBINATORICS SEMINAR

Tuesdays, Thursdays      2:00        Parker 328



2014 - 2015

 

Tuesday, May 19

Speaker: Selda Kucukcifci, Koc University, Turkey,

Title: Uniformly Resolvable H-Designs



Thursday, May 21

Speaker: Sibel Ozkan, Gebze Technical University, Turkey

Title: On the Hamilton-Waterloo Problem



Tuesday, April 21

Speaker: Mariusz Meszka, AGH University of Science and Technology, Krakow, Poland

Title: Palettes in block colorings of some combinatorial structures

 

Thursday, April 16

Speaker: Alex Rosa, McMaster University

Title: A possible analogue of $\rho$-labelings for 3-hypergraphs

Tuesday, April 14 

Speaker: Joshua Harrelson

Subject: Forest decompositions

 

Thursday, April 2

Speaker: Liz McInnis

Title: Tilings of graphs



Tuesday, March 31

Speaker: Jennifer Aust

Title: Bounded Complete Embedding Graphs

Thursday, March 12

Speaker: A J W Hilton, University of Reading and Queen Mary College University of London, UK

Abstract: We generalize Hall's Condition for a system of distinct representatives and apply it to obtain results about completing latin squares. A latinized square is a generalization of a latin square. We have a set v1,v2,.....,vn of positive integers and a positive integer p such that v1 + v2 + .......+vn = p^2 and 1 <= vi <=p.  A p x p array on symbols x1, x2, ......,xn such that each xi occurs vi times, and no xi occurs twice in any row or column is a (v1,v2,......,vn)-latinized square. We give some completion results for this type of square. 

 

Thursday, March 19

Speaker: James Hammer

Title: TBA

Thursday, February 26

Speaker: Pete Johnson

Title: Minimum (n,k,t) graphs

Abstract: Suppose that n, k, and t are positive integers, in non-increasing order. An (n,k,t) graph is a simple graph on n vertices such that every induced subgraph on k vertices has a complete subgraph on t vertices. A minimum (n,t,k)graph is an (n,k,t)graph with the minimum number of edges possible for such a graph. The case t = 2 is intriguing because the unique minimum (n,k,2) graph is the complemenet of the Turan graph on n vertices with k - 1 parts, by Turan's theorem.

Our (Dean Hoffman's, Jessica McDonald's, and my) conjecture is that for every n, k,and t, there is a minimum (n,k,t) graph whose every component is a clique--call it a cligue graph, for short. This talk will show how to obtain, for each n, k, and t,  all graphs with the minimum number of edges among (n,k,t) graphs which are clique graphs.

Tuesday, February  24

Speaker: ABBALABBA

Title: Fractional isomorphisms of Cayley graphs

 

Tuesday, February 17

Speaker: Dean Hoffman

Topic: A nice NP_Complete argument for a digraph problem

Tuesday, February 10

Speaker: Vitaly Voloshin,Troy University

Topic: Hypertrees and cycles in hypergraphs

Abstract: A hypertree is a hypergraph isomorphic to a family of sub trees of a tree. In hypergraphs, hypertrees play a role similar to the role of trees in graphs with the only distinction: it is MUCH MORE interesting!  We will discuss some properties of hypertrees and their relation to other remarkable classes of hypergraphs.

 

Thursday, February 5

Topic: CCL, An open problem on 5-cycle systems

Thursday, January 22

Speaker: Pete Johnson

Title:  Some problems concerning the secure-domination numbers of graphs

Tuesday, January 20

Speaker: Dean Hoffman

Topic: A puzzle I can't seem to solve!


Tuesday, December 2

Combinatorics faculty meeting.....courses for next year. Be there or be square!

 

Thursday, November 20

Speaker: Suil O, Georgia State University

Title: Edge-connectivity in regular multigraphs from eigenvalues 

 

Tuesday, November 4

Speaker: Amin Bahmanian

Title: Extending factorizations of complete uniform hypergraphs 

 

Thursday, October 30

Speaker: Vitaly Voloshin, Troy University

Topic: Some open problems in hypergraph coloring

Tuesday, October 21

Speaker: Jessica McDonald

Title:  A list analog of Vizing's Theorem for simple graphs with triangles but no other odd cycles

 

Tuesday, October 14

Speaker: Curt Lindner

Topic: How to embed a partial odd cycle system

Thursday, October 9

NO SEMINAR

 

Tuesday, September 30

Speaker: Pete Johnson

Topic: Later developments concerning Hall's Condition and list coloring


Thursday, September 25

NO SEMINAR

 

Tuesday, September 23

Speaker: Pete Johnson

Topic: Another chapter in the history of list-coloring

 

Thursday, September 18

Topic: CCL, Graph theory and universal algebra go hand in hand!


Tuesday, September 16

NO SEMINAR

 

Thursday, September 11

Speaker: Doug Leonard

Topic: Coordinates other than affine or projective

 

Tuesday, September 9

Speaker: Pete Johnson

 

Thursday, September 4

Speaker: Dean Hoffman, continued

 

Tuesday, September 2

NO SEMINAR

 

Thursday, August 28

Speaker: Saad El-Sanati, Illinois State University

Title: On decomposing regular graphs and multigraphs into isomorphic trees and forests

 

Tuesday, August 26

Speaker: Dean Hoffman

Thursday, August 21

Title:  CCL, How to squash a 6-cycle system into a Steiner triple system

Tuesday, August 19

ORGANIZATIONAL MEETING

 

Last updated: 04/23/2015