
Displaying from Friday, April 05, 2013

April 2013

Friday 05 
15:00  SEMINAR  Groups and Combinatorics Seminar, Redeipolynomials in finite geometry

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Abstract:
L. Redei has studied in a detailed way socalled "lacunary" polynomials over finite fields. One of the applications described is to investigate the number of values the difference quotient of a polynomial over a finite field can have. This result has a direct (...)

Tuesday 09 
13:00  SEMINAR  Groups and Combinatorics Seminar, The ErdosStone Theorem for finite geometries

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Abstract:
For any class of graphs, the growth function h(n) of the class is defined to be the maximum number of edges in a graph in the class on n vertices. The ErdosStone Theorem remarkably states that, for any class of graphs that is closed under taking subgraphs, the asymptotic (...)

Friday 12 
15:00  SEMINAR  Groups and Combinatorics Seminar, On the number of matroids

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Abstract:
Matroids are combinatorial structures that generalize graphs as well as configurations of points in projective space. They consist of a finite ground set E and a set of subsets of E called B, such that B satisfies certain axioms. We consider the problem of bounding the number (...)

Friday 19 
15:00  SEMINAR  Groups and Combinatorics Seminar, Arctransitive graphs with large automorphism groups

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Abstract:
An arc in a graph is an unordered pair of adjacent vertices. A graph is called arctransitive if its automorphism group acts transitively on its set of arcs. We consider the problem of bounding the size of the automorphism group of an arctransitive graph in terms of its order (...)

Friday 26 
15:00  SEMINAR  Groups and Combinatorics Seminar, Locally sarc transitive regular covers of complete bipartite graphs

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Abstract:
The normal quotient method has made the study of certain families of finite graphs (for instance, sarc transitive and locally sarc transitive graphs) more approachable by dividing the problem into two parts:
(I) Study the "basic graphs," those graphs in the family (...)


May 2013

Friday 03 
15:00  SEMINAR  Groups and Combinatorics Seminar, On metacirculants The relationship of weak metacirculants and metacirculants

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Metacirculants were introduced by Alspach and Parsons in 1982 and have been a rich source of various topics since then, including the Hamiltonian path problem of vertextransitive graphs. A metacirculant has a vertextransitive metacyclic subgroup of automorphisms, and a longstanding curious (...)

Friday 10 
15:00  SEMINAR  Groups and Combinatorics Seminar, Ovoids and spreads of finite polar spaces

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Abstract:
This talk is a survey of one of the driving topics in finite geometry, and the connections that ovoids and spreads have to other areas of finite geometry and permutation groups. Apart from a presentation of the history of the field and the main open problems, the speaker will (...)

Friday 17 
15:00  SEMINAR  Groups and Combinatorics Seminar, Local transitivity properties of graphs and pairwise transitive designs

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Abstract:
One of the earliest triumphs in applying the finite simple group classification in algebraic graph theory was the characterization of finite distance transitive graphs. Recent work by Devillers, Giudici, Li and myself focuses on a generalisation of this class of graphs: locally (...)

Friday 24 
15:00  SEMINAR  Groups and Combinatorics Seminar, Algebraic graph theory applied to configurations of polar spaces

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Abstract:
The speaker will give the second half of his talk from a fortnight ago, but with a different context. We will first go through some background on the basics of algebraic graph theory, eigenvalue techniques, and strongly regular graphs, before giving some short nonexistence (...)

Friday 31 
15:00  SEMINAR  Groups and Combinatorics Seminar, (k,L)complexes and graph symmetry

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Abstract:
Given an integer k and a graph L, a (k,L)complex is a polygonal complex consisting of vertices, edges and faces such that each face is a regular kgon and the graph induced by the edges and faces at each vertex is isomorphic to L. Many questions about the existence and (...)


June 2013

Friday 07 
15:00  SEMINAR  Groups and Combinatorics Seminar, The Merino Welsh Conjecture

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Abstract:
Merino and Welsh conjectured that for any loopless bridgeless graph, the number of spanning trees is dominated either by the number of acyclic orientations of the graph, or by the number of totally cyclic orientations of the graph.
In this talk, I will discuss this (...)

Friday 14 
15:00  SEMINAR  Groups and Combinatorics Seminar, Recognising the Symmetric and Alternating Squares

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Abstract:
The fundamental goal of Computational Group Theory is recognition: given a group somehow represented in a computer (usually by generators), determine any information about the group that you can, as quickly as possible. This is `easy' if we have enough time and memory to write (...)

Friday 21 
This week the seminar will consist of three 20 minute talks, starting at 3pm Friday 21st of June in Blakers Lecture Theatre.
Talk 1
Mark Ioppolo
will speak on
Symmetry in coding theory: Constructing error control codes with group theory
Abst (...)


July 2013

Friday 05 
15:00  SEMINAR  Groups and Combinatorics Seminar, On PseudoInjective Group Algebra

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Abstract:
A module M is called pseudoinjective if for every submodule X of M, any monomorphism f : X > M can be extended to a homomorphism g : M > M. Let K be a field and G a group. It is well known that a group algebra K[G] is selfinjective if and only if the group (...)


August 2013

Friday 02 
15:00  SEMINAR  Groups and Combinatorics Seminar, Maximal arcs that contain regular hyperovals

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Abstract:
A maximal narc is a set of q(n1) + n points in a projective plane such that any line of the plane meets 0 or n of them. The most common maximal arcs, called the Mathon arcs, are constructed by taking the union of regular hyperovals. In particular, there are no known maximal 4 (...)

Friday 09 
15:00  SEMINAR  Groups and Combinatorics Seminar, Semisymmetric graphs of prime valency

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Abstract:
A graph is called Xsemisymmetric if the group X acts transitively on edges, but not on vertices. Such graphs are necessarily bipartite and biregular, of valencies k and l say. There is a natural relationship between semisymmetric graphs and amalgams of groups. This leads us (...)

Sunday 11 
10:00  OPEN DAY  2013 Open Day : Join us for our Centenary Open Day and experience all that UWA has to offer

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Come and find out about our undergraduate and postgraduate courses, career options, scholarship opportunities, our valuable research, community programs and facilities.
There's also residential college tours, handson activities, live music, entertainment, and plenty of fun activities (...)

Friday 16 
15:00  SEMINAR  Groups and Combinatorics Seminar, Decomposing tensor products over fields of small characteristic

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Abstract:
One motivation for this talk comes from representation theory: decomposing a tensor product of irreducible (or indecomposable) representations as a sum of smaller degree irreducible (or indecomposable) representations. Other motivations come from quantum mechanics and (...)

Friday 23 
15:00  SEMINAR  Groups and Combinatorics Seminar, Breaking symmetries of infinite graphs

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Abstract:
Symmetry breaking involves colouring the elements of a combinatorial structure so that the resulting structure has no nontrivial symmetries. In this talk I'll give an introduction to symmetry breaking, with a particular focus on infinite graphs. I'll also discuss a number of (...)

Friday 30 
15:00  SEMINAR  Groups and Combinatorics Seminar, The structure of 3separations of matroids

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Abstract:
In this talk, I will give an introduction to decomposition theory of 3connected matroids. In order to make it more accessible I will also introduce some related definitions and examples.


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