Invited by Prof. Shoujun Xu of the School of Mathematics and Statistics, Prof. Marston Conder from University of Auckland will visit our school and give a series of lectures from October 17th to October 20th in 2019.

Title1: Symmetry and chirality in discrete structures

Time：14:30 p.m., October 17th, 2019

Location：Room B503, Tianshan Building,Yuzhong

Abstract: Symmetry is pervasive in both nature and human culture. The notion of chirality (or 'handedness') is similarly pervasive, but less well understood.In this lecture, which is dedicated to my late colleague Peter Lorimer,I will talk about a number of situations involving discrete objects that have maximum possible symmetry in their class, or maximum possible rotational symmetry while being chiral. Examples include combinatorial graphs (networks), geometric solids, maps on surfaces, and some other more abstract structures. These will be illustrated by pictures as much as possible.

Title2: Some new approaches to finding the minimum genus of a graph

Time：10:30 a.m., October 18th, 2019

Location：Room 911, Qiyun Building

Abstract: The genus of a connected graph $X$ is defined as the smallest genus of those compact orientable surfaces into which $X$ has a 2-cell embedding (breaking up the surface into `faces'). For example, planar graphs are precisely those having genus $0$.

In this talk I'll describe some recent work that helps find the minimum genus of certain graphs (also in the non-orientable case), when traditional methods are not helpful. One new method uses the orbits of the automorphism group of the graph on cycles of small length, as candidates for bounding cycles of faces of the embedding.

This turned out to be helpful in finding the small genus embeddings of several graphs of interest, and then in combination with two other new approaches for eliminating smaller genera (using independence numbers and integer linear programming), led to the answers to a many open questions.

Curriculum Vitae

Marston Conder，DPhil at the University of Oxford (1980) on minimal generating pairs for permutation groups, under the supervision of Prof. Graham Higman FRS.Postdoctoral fellowships at University of Otago (1981) and Universität Tübingen (1982).He got academic positions at University of Auckland since 1983, promoted to full Professor in 1993, Distinguished Professor in 2012.His research interests are Combinatorial group theory ,Symmetries of graphs, maps, polytopes, surfaces and other discrete objects ,Discrete computation.He has won Hector Medal, Royal Society of New Zealand, 2014 ,Jones Medal, Royal Society of New Zealand, 2018 and Research Excellence Medal (for work in last 5 years), University of Auckland, 2019 .He is the chair of Budget Committee, University of Auckland, since 2000 and the convenor of Algebra & Combinatorics group, Maths Department, University of Auckland, since 2018.

Welcome to attend!

Provincial Key Laboratory of Applied Mathematics and Complex Systems,Gansu Province

School of mathematics and statistics

CuiyingHonors College

October 16th, 2019