# The Combinatorics Group: Seminars

Every week or two during the Fall and Winter semesters we have a Combinatorics Seminar. Refreshments are frequently provided.

Speakers and topics for the present semester (and recent semesters) are shown below.

Presentations listed in *italics* were given as Colloquia.

## Fall 2012

Date | Speaker |
Topic |

Friday, 2 November |
Gena Hahn, Universite de Montreal |
Cops and robbers on graphs - finite and infinite |

## Summer 2012

Date | Speaker |
Topic |

Friday, 29 June |
Daniel Horsley, Monash University |
Compressed sensing and hash families |

## Winter 2012

Date | Speaker |
Topic |

Wednesday, 14 March |
Ryan Tifenbach, Memorial University of Newfoundland |
Spectral graph theory I |

Wednesday, 21 March |
Rebecca Milley, Dalhousie University | Lessons in Losing: An Introduction to Misere Game Theory |

Wednesday, 28 March |
Ryan Tifenbach, Memorial University of Newfoundland |
Spectral graph theory II |

## Winter 2011

Date | Speaker |
Topic |

Wednesday, 23 March |
Jared Howell, Memorial University of Newfoundland |
The Intersection of Latin Squares |

## Summer 2010

Date | Speaker |
Topic |

Tuesday, 31 August |
Colin Reid, McMaster University |
T-chromatic index for Steiner S(2; k; v)s |

## Winter 2010

Date | Speaker |
Topic |

Monday, 15 February |
Robert Bailey, University of Regina |
Hamiltonian decompositions of hypergraphs |

Friday, 26 February |
Andrea Burgess, Memorial University of Newfoundland |
Cycle decompositions of some families of graphs |

Friday, 05 March |
Daniel Horsley, Memorial University of Newfoundland |
Nimber Theory: Impartial Combinatorial Games - I |

Friday, 12 March |
Daniel Horsley, Memorial University of Newfoundland | Nimber Theory: Impartial Combinatorial Games - II |

Friday, 09 April |
Robert Gallant, Sir Wilfred Grenfell College | Finding discrete logarithms using additional information |

## Fall 2009

Date | Speaker |
Topic |

Thursday, 08 October |
Dariusz Dereniowski, Gdansk University of Technology |
Nonclassical measures for evaluating search strategies |

Thursday, 15 October |
Daniel Horsley, Memorial University of Newfoundland |
Embedding partial Steiner triple systems |

Thursday, 22 October |
Asiyeh Sanaei, Memorial University of Newfoundland |
Rectilinear Symmetric Crossing Number of Complete Graphs |

Thursday, 05 November |
J.C. Loredo-Osti, Memorial University of Newfoundland |
Trees of descent, Steiner trees and the computation of likelihood in complex genealogies |

Thursday, 03 December |
Andrew Jesso, Memorial University of Newfoundland |
The Hamiltonicity of Block-Intersection Graphs of Balanced Incomplete Block Designs |

Friday, 11 December | Rebecca Keeping, Memorial University of Newfoundland | The Watchman's Walk Problem and its Variations |

## Summer 2009

Date | Speaker |
Topic |

Friday, 31 July |
Adrian Vetta, McGill University |
Paths, viruses, and galaxy cutsets |

## Winter 2009

Date | Speaker |
Topic |

Friday, February 13th |
Oznur Yasar Diner, Memorial University of Newfoundland |
Forbidden Minor Constructions for 4-Searchable Series-Parallel Graphs |

Friday, February 20th |
David Pike, Memorial University of Newfoundland |
Phylogenetic Networks for Human mtDNA Haplogroup T |

Friday, February 27th |
Danny Dyer, Memorial University of Newfoundland |
Cyclic perfect $T(P_2 cup P_2 cup P_2)$ triple systems |

Friday, March 13th | Nabil Shalaby, Memorial University of Newfoundland |
Skolem-Langford Type Sequences |

Friday, March 20th | Ahmed Ababheh, Memorial University of Newfoundland |
Disjoint starter sequences |

Tuesday, April 28th |
Rebecca Keeping, Memorial University of Newfoundland |
The Watchman's Walk Problem with Time Restraints |

## Fall 2008

Date | Speaker | Topic |

Thursday, September 11th |
Dominique de Werra, École Polytechnique Fédérale de Lausanne |
Graph transformations and peseudoboolean reduction |

Thursday, September 18th |
David Pike, Memorial University of Newfoundland |
Hamiltonicity and Restricted Block-Intersection Graphs of t-Designs |

Thursday, September 25th |
Dariusz Dereniowski, Gdansk University of Technology |
Using edge rankings for searching in partial orders |

Thursday, October 2nd |
Daniel Horsley, Memorial University of Newfoundland |
A solution to Alspach's problem for complete graphs of large odd order |

Thursday, October 9th |
Edgar Goodaire, Memorial University of Newfoundland |
Group-based Latin Squares |

Thursday, October 16th |
Rebecca Keeping, Memorial University of Newfoundland |
Maximum k-Limited Packings in Trees |

Thursday, October 23rd |
Danny Dyer, Memorial University of Newfoundland |
Two coloured path decompositions |

Tuesday, October 28rd |
Rebecca Keeping, Memorial University of Newfoundland |
A Review of the Watchman's Walk Problem |

## Summer 2008

Date | Speaker | Topic |

Wednesday, July 9th |
Vaclav Linek, University of Winnipeg |
Octahedral Designs |

Tuesday, August 19th |
Nancy Clarke, Acadia University |
Variations of the Cops and Robber Game Played with Imperfect Information |

Wednesday, August 20th |
Boting Yang, University of Regina |
Edge Searching on Cycle-Disjoint Graphs |

Wednesday, August 20th |
Pawel Pralat, Dalhousie University |
Cleaning d-regular graphs with brushes |

## Winter 2008

Date | Speaker | Topic |
---|---|---|

Wednesday, Feb 13th |
Daniela Silvesan, Memorial University |
The spectrum of Skolem and hooked Skolem sequences with prescribed pairs in common |

Friday, Feb 29th |
Oznur Yasar Memorial University |
Fast Search is Linear for Trees |

Wednesday, May 7th |
Laura Chavez-Lomeli, Simon Fraser University |
Chromatic and flow number for matroids |

## Winter 2007

Date | Speaker | Topic |
---|---|---|

Friday, Jan 26th |
Vaclav Linek, University of Winnipeg |
Langford sequences: parametrizations, commutative diagrams and quotients |

## Fall 2006

Date | Speaker | Topic |
---|---|---|

Tuesday, Oct 31st |
Josh Manzer Memorial University |
Skolem labeling of generalized windmill graphs |

## Spring 2006

Date | Speaker | Topic |
---|---|---|

Thursday, May 11 |
Brian Alspach, University of Regina |
Groups acting on graphs |

Thursday, Jun 15 |
Gary MacGillivray, University of Victoria |
Circular colourings of hypergraphs |

Tuesday, Aug 8 |
Shinya Fujita, Gunma National College of Technology (Japan) |
Recent results on vertex-disjoint cycles in graphs |

Tuesday, Aug 15 |
Shinya Fujita, Gunma National College of Technology (Japan) |
Non-separating subgraphs in highly connected graphs |

## Winter 2006

Date | Speaker | Topic |
---|---|---|

Thursday, Feb 16 |
Sueng-Byond (Light) Go, Memorial University |
Cyclic Steiner triple systems with cyclic subsystems |

Thursday, Mar 2 |
Yubo Zou, Memorial University |
Dominating hypercubes |

Thursday, Apr 6 |
Brenda Wicks, Memorial University |
Graceful labelings of triangular cacti graphs |

Thursday, Apr 20 |
Oznur Yasar, Memorial University |
Edge searching weighted graphs |

## Fall 2005

Date | Speaker | Topic |
---|---|---|

Friday, Nov 18 |
Colin Reid, Memorial University |
Near-lambda-fold Skolem sequences and infinite Skolem sequences |

Friday, Nov 25 |
Yubo Zou, Memorial University |
Decycling Fibonacci cubes |

## Spring 2005

Date | Speaker | Topic |
---|---|---|

Thursday, Jun 30 |
Danny Dyer, University of Regina |
Isomorphic factorizations of circulant graphs |

## Winter 2005

Date | Speaker | Topic |
---|---|---|

Friday, Feb 25 |
Oliver Ittig, Swiss Federal Institute of Technology |
Scheduling with multiprocessors: A rounding network algorithm with a constant error |

## Fall 2004

Date | Speaker | Topic |
---|---|---|

Tuesday, Nov 2 |
Nabil Shalaby, Memorial University |
Skolem-type rectangles |

Tuesday, Nov 9 |
Yubo Zou, Memorial University |
Decycling of Cartesian product of cycles |

Tuesday, Nov 16 |
David Morgan, University of Alberta |
Useful vertex names: Informative labelling schemes for graphs |

Tuesday, Nov 23 |
Andrea Burgess, Memorial University |
Invariants for even cycle systems |

Tuesday, Nov 30 |
Colin Reid, Memorial University |
The existence of looped m-near-Skolem sequences |

## Spring 2004

Date | Speaker | Topic |
---|---|---|

Friday, Jun 18 |
Danny Dyer, Simon Fraser University |
Using cliques to sweep graphs |

## Fall 2003

Date | Speaker | Topic |
---|---|---|

Thursday, Oct 16 |
Eddie Cheng, Oakland University |
An introduction to linear integer programming via the stable set problem |

## Spring 2003

Date | Speaker | Topic |
---|---|---|

Wednesday, Jul 2 |
Danny Dyer, Simon Fraser University |
Two-coloured path decompositions |

## Winter 2003

Date | Speaker | Topic |
---|---|---|

Tuesday, Feb 4 |
Rolf Rees, Memorial University |
Constructing Steiner triple systems for all admissible orders - Part I |

Tuesday, Feb 18 |
Rolf Rees, Memorial University |
Constructing Steiner triple systems for all admissible orders - Part II |

Tuesday, Mar 25 |
Nabil Shalaby, Memorial University |
Skolem-type sequences |

Tuesday, Apr 1 |
Rolf Rees, Memorial University |
Constructing Steiner triple systems for all admissible orders - Part III |

## Spring 2002

Date | Speaker | Topic |
---|---|---|

Friday, Aug 9 |
Martin Grüttmüller, University of Rostock (Germany) |
Completing partial Latin squares with prescribed diagonals |

Wednesday, Aug 14 |
Gennian Ge, Suzhou University (P.R. China) |
Whist tournaments |

## Winter 2002

Date | Speaker | Topic |
---|---|---|

Wednesday, Jan 30 |
Eric Moorhouse, University of Wyoming |
Projective planes - Part I |

Wednesday, Feb 6 |
Eric Moorhouse, University of Wyoming |
Projective planes - Part II |

Wednesday, Feb 20 |
Nabil Shalaby, Memorial University |
Disjoint Skolem sequences |

Wednesday, Mar 6 |
Rolf Rees, Memorial University |
Embedding cyclic partial Steiner triple systems |

Wednesday, Mar 27 |
Patrick Fleming, University of Wyoming |
Generating functions |

Wednesday, Apr 3 |
Alasdair Graham, Memorial University |
A survey of packings and coverings of simple graphs |

Wednesday, Apr 3 |
Aygul Mamut, Memorial University and Xinjiang University |
Decompositions of graphs into 1-factors |

Thursday, Apr 4 |
Chao Zhong, Memorial University |
Perfect graphs |

## Fall 2001

Date | Speaker | Topic |
---|---|---|

Monday, Sep 10 |
Sarah Mathews, Memorial University |
Configurations in Steiner triple systems |

Wednesday, Sep 19 |
Rolf Rees, Memorial University |
On holes in t-designs - Part I |

Thursday, Sep 27 |
Vaclav Linek, University of Winnipeg |
Pattern avoidance: The Abelian case |

Wednesday, Oct 3 |
Rolf Rees, Memorial University |
On holes in t-designs - Part II |

Wednesday, Oct 17 |
Alasdair Graham, Memorial University |
Skolem labelled graphs |

Wednesday, Oct 31 |
Eric Moorhouse, University of Wyoming |
The transfer matrix method |

Wednesday, Nov 21 |
Eddie Cheng, Oakland University |
Submodular functions, polymatroids and strength |

Friday, Nov 30 |
Joanna Ellis-Monaghan, University of Vermont |
An introduction to the Tutte polynomial |

## Winter 2001

Date | Speaker | Topic |
---|---|---|

Tuesday, Feb 6 |
Nabil Shalaby, Memorial University |
Skolem labelled graphs |

Tuesday, Feb 13 |
Michael Parmenter, Memorial University |
Applications of graph theory to the study of DNA and RNA chains (1) |

Tuesday, Feb 20 |
Michael Parmenter, Memorial University |
Applications of graph theory to the study of DNA and RNA chains (2) |

Tuesday, Mar 13 |
Rolf Rees, Memorial University |
A survey of Kirkman designs (2) |

Tuesday, Mar 20 |
David Morgan, Memorial University |
Domination in graphs (1) |

Tuesday, Mar 27 |
A.E. Fekete, Memorial University |
Spectral sequences of integers |

Tuesday, Apr 10 |
David Pike, Memorial University |
A cryptographic application of graph theory |

Tuesday, Apr 17 |
David Morgan, Memorial University |
Domination in graphs (2) |

Tuesday, Apr 24 |
David Morgan, Memorial University |
Gracefully labelled trees from Skolem and related sequences |

Wednesday, Apr 25 |
Alex Rosa, McMaster University |
Large sets of Steiner triple systems |

## Fall 2000

Date | Speaker | Topic |
---|---|---|

Tuesday, Sep 19 |
Eugene Lilly, Memorial University |
Mutually orthogonal Latin squares |

Tuesday, Sep 26 |
Sarah Mathews, Memorial University |
Cyclically indecomposable two-fold triple systems from Skolem sequences |

Tuesday, Oct 3 |
Robin Swain, Memorial University |
8-cycle decompositions of the Cartesian product of two complete graphs |

Tuesday, Oct 10 |
Vesselin Dresnky, Bulgarian Academy of Sciences |
Applications of the pigeon hole principle |

Tuesday, Oct 17 |
Rolf Rees, Memorial University |
A survey of Kirkman designs (1) |

Tuesday, Oct 24 |
David Morgan, Memorial University |
A survey of graceful labelings |

## Winter 2000

Date | Speaker | Topic |
---|---|---|

Thursday, Feb 17 |
Michael Parmenter, Memorial University |
On groups with redundancy in multiplication |

Thursday, Mar 2 |
Rolf Rees, Memorial University |
Magic labelings of graphs |

## Fall 1999

Date | Speaker | Topic |
---|---|---|

Thursday, Nov 4 |
Nabil Shalaby, Memorial University |
Optimal complementary coverings of the complete graphs by paths of length three |

Thursday, Nov 23 |
Yuri Bahturin, Memorial University, and Victor Petrogradsky, Ul'yanovsk State University (Russia) |
Young diagrams, generating functions and proper identities II |

Thursday, Dec 2 |
David Morgan, Memorial University |
Applications of Polya's counting theorem in chemical compounds |

## Winter 1999

Date | Speaker | Topic |
---|---|---|

Thursday, Jan 26 |
Nabil Shalaby, Memorial University |
Skolem sequences and applications - I |

Tuesday, Feb 2 |
Nabil Shalaby, Memorial University |
Skolem sequences and applications - II |

Tuesday, Feb 9 |
David Pike, Memorial University |
Perfect 1-factorisations - I |

Tuesday, Feb 16 |
David Pike, Memorial University |
Perfect 1-factorisations - II |

Tuesday, Mar 2 |
David Morgan, Memorial University |
Graceful labelings of graphs - II |

## Fall 1998

Date | Speaker | Topic |
---|---|---|

Tuesday, Sep 29 |
Tara Stuckless, Memorial University |
The existence of looped Langford sequences |

Tuesday, Oct 6 |
David Pike, Memorial University |
Decomposing block-intersection graphs of Steiner triple systems into triangles - I |

Tuesday, Oct 20 |
David Pike, Memorial University |
Decomposing block-intersection graphs of Steiner triple systems into triangles - II |

Tuesday, Oct 27 |
Antal Fekete, Memorial University |
Step-numbers and their applications - I |

Tuesday, Nov 3 |
Antal Fekete, Memorial University |
Step-numbers and their applications - II |

Tuesday, Nov 10 |
Antal Fekete, Memorial University |
Step-numbers and their applications - III |

Tuesday, Nov 17 |
Antal Fekete, Memorial University |
Step-numbers and their applications - IV |

Tuesday, Nov 24 |
David Morgan, Memorial University |
Graceful labelings of graphs - I |