Coxeter groups arise in a wide variety of areas, so every mathematician should know some basic facts about them, including their connection to "Dynkin diagrams." Proofs about these "groups generated by reflections" mainly use group theory, geometry, and combinatorics.
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Location: B660 University Hall Web page: http://www.cs.uleth.ca/~nathanng/ntcoseminar/ Dave Morris, University of Lethbridge