**SMS scnews item created by Boris Lishak at Tue 19 Mar 2019 1525**

Type: Seminar

Modified: Tue 19 Mar 2019 1530

Distribution: World

**Calendar1: 26 Mar 2019 1400-1500**

**CalLoc1: Carslaw 535A**

CalTitle1: Liebenau -- On Ramsey equivalence in graph theory

Auth: borisl@dora.maths.usyd.edu.au

### Geometry and Topology Seminar

# On Ramsey equivalence in graph theory

### Anita Liebenau (UNSW)

Please join us for lunch before the talk. We are meeting at 12:45 on Carslaw level 2.
**Abstract:**
In this talk I will introduce the notion of Ramsey equivalence of two graphs and showcase one or two proofs to illustrate the methods in this field. A graph G is called Ramsey for H if every red/blue-colouring of the edges of G produces a monochromatic copy of H. Two graphs H and H’ are called Ramsey equivalent if every graph G is either Ramsey for both H and H’, or for neither of them. This notion was introduced only in 2010, but arises naturally when studying properties of graphs G that are minimal with respect to being Ramsey for a fixed graph H. Interestingly, the complete graph is not Ramsey equivalent to any other connected graph but itself. My aim is to make this a gentle introduction, so not much previous knowledge on graphs or on Ramsey theory is assumed.