Yoshikata Kida

  1. The co-Hopfian property of surface braid groups.

    Authors: Yoshikata Kida, Saeko Yamagata
    Subjects: Group Theory
    Abstract

    When both g and p are integers at least two, we give a description of any
    injective homomorphism from a finite index subgroup of the braid group with p
    strings on a closed orientable surface of genus g, into the braid group. As a
    consequence, we show that any finite index subgroup of the braid group is
    co-Hopfian.

  2. Injections of the complex of separating curves into the Torelli complex.

    Authors: Yoshikata Kida
    Subjects: Group Theory
    Abstract

    We show that for most of compact orientable surfaces, any superinjective map
    from the complex of separating curves into the Torelli complex is induced from
    an element of the extended mapping class group. As an application, we prove
    that any injective homomorphism from a finite index subgroup of the Johnson
    kernel into the Torelli group for such a surface is induced from an element of
    the extended mapping class group.

  3. The co-Hopfian property of the Johnson kernel and the Torelli group.

    Authors: Yoshikata Kida
    Subjects: Group Theory
    Abstract

    For most of compact orientable surfaces, we show that any superinjective map
    from the complex of separating curves into itself is induced from an element of
    the extended mapping class group. We apply this result to proving that any
    finite index subgroup of the Johnson kernel is co-Hopfian. The same properties
    are shown for the Torelli complex and the Torelli group.

  4. Automorphisms of the Torelli complex and the complex of separating curves.

    Authors: Yoshikata Kida
    Subjects: Group Theory
    Abstract

    We compute the automorphism groups of the Torelli complex and the complex of
    separating curves for most of compact orientable surfaces. As an application,
    we show that the commensurators of the Torelli group and the Johnson kernel for
    such surfaces are naturally isomorphic to the extended mapping class group.

RSS-материал