On Vizing’s Edge Colouring Question

by Marthe Bonamy

Abstract:

In his 1965 seminal paper on edge colouring, Vizing proved that a (\Delta+1)-edge colouring can be reached from any given proper edge colouring through a series of Kempe changes, where \Delta is the maximum degree of the graph. He concludes the paper with the following question: can an optimal edge colouring be reached from any given proper edge colouring through a series of Kempe changes? In other words, if the graph is \Delta-edge-colourable, can we always reach a \Delta-edge-colouring? If true, this would imply a more recent conjecture of Mohar (2006) that in any graph, all (\Delta+2)-edge-colourings are equivalent up to a series of Kempe changes. We discuss recent progress around these questions.

Event Timeslots (1)

Tuesday
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Marthe Bonamy