r-fundamental groups and r-covering maps of graphs

Date: 
2014/05/12 Mon 15:00 - 16:30
Room: 
Room 609, Building No.6
Speaker: 
Takahiro Matsushita
Affiliation: 
The University of Tokyo
Abstract: 

For a positive integer r, we introduce the r-fundamental groups and the r-covering maps of graphs. r-fundamental groups are applied to the existence problem of graph homomorphisms. Especially, in the case r=2, these are closely related to the neighborhood complex considered in the graph coloring problem.