SEMINAR: Groups and Combinatorics Seminar: Idempotent generation and road closures
|Groups and Combinatorics Seminar: Idempotent generation and road closures
Time and place: 16:00 Friday 23 September in Blakers LT
Speaker: Peter Cameron (St. Andrews)
Title: Idempotent generation and road closures
Abstract: This is part of a big project linking the properties of a transformation semigroup to those of the permutation group forming its group of units. The particular question I am discussing is this: For which permutation groups $G$ is it the case that, for any transformation $a$ of rank 2, the semigroup $ angle G,a
angle etminus G$ is generated by its idempotents? Such a group must be primitive, but not all primitive groups have this property. It turns out to be equivalent to the property that, for any orbital graph for $G$ (regarded as a road network), if we close the edges in a block of imprimitivity for the action of $G$, the network remains connected. We have a conjecture about the primitive groups which satisfy this condition. This is joint work with Joćo Arajśo (Lisbon).
Fri, 23 Sep 2016 16:00
Fri, 23 Sep 2016 17:00
Tomasz Popiel <[email protected]>
Mon, 19 Sep 2016 14:01
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