Isao Hasegawa (University of Tokyo)
Title: Monodromies on a punctured disk

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Abstract:
A surface braid is a total space of a branched covering on the two disk with some more conditions. One of tools studying surface braids is a surface braid monodromy which is a homomorphism from the fundamental group of a punctured disk to an $m$-strand braid group. In this talk, using another homomorphism, we find out whether some of surface braids are non-ribbon.