8 citations · 35 across the 10 of their papers we have counts for
10 papers
On relative hyperbolicity for a group and relative quasiconvexity for a subgroup
Yoshifumi Matsuda, Shin-ichi Oguni, Saeko Yamagata
We consider two families of subgroups of a group. Each subgroup which belongs to one family is contained in some subgroup which belongs to the other family. We then discuss relatio…
Notes on relatively hyperbolic groups and relatively quasiconvex subgroups
Yoshifumi Matsuda, Shin-ichi Oguni, Saeko Yamagata
We define relatively quasiconvex subgroups of relatively hyperbolic groups in the sense of Osin and show that such subgroups have expected properties. Also we state several definit…
Blowing up and down compacta with geometrically finite convergence actions of a group
Yoshifumi Matsuda, Shin-ichi Oguni, Saeko Yamagata
We consider two compacta with minimal non-elementary convergence actions of a countable group. When there exists an equivariant continuous map from one to the other, we call the fi…
Hyperbolically embedded virtually free subgroups of relatively hyperbolic groups
Yoshifumi Matsuda, Shin-ichi Oguni, Saeko Yamagata
We show that if a group is not virtually cyclic and is hyperbolic relative to a family of proper subgroups, then it has a hyperbolically embedded subgroup which contains a finitely…
The universal relatively hyperbolic structure on a group and relative quasiconvexity for subgroups
Yoshifumi Matsuda, Shin-ichi Oguni, Saeko Yamagata
We discuss the notion of the universal relatively hyperbolic structure on a group which is used in order to characterize relatively hyperbolic structures on the group. We also stud…
-simplicity for groups with non-elementary convergence group actions
Yoshifumi Matsuda, Shin-ichi Oguni, Saeko Yamagata
We prove that a countable group with an effective minimal non-elementary convergence group action is a Powers group. More strongly we prove that it is a strongly Powers group and t…
Automorphisms of the Torelli complex for the one-holed genus two surface
Yoshikata Kida, Saeko Yamagata
Let S be a connected, compact and orientable surface of genus two having exactly one boundary component. We study automorphisms of the Torelli complex for S, and describe any isomo…
The co-Hopfian property of surface braid groups
Yoshikata Kida, Saeko Yamagata
Let g and n be integers at least two, and let G be the pure braid group with n strands on a closed orientable surface of genus g. We describe any injective homomorphism from a fini…
Commensurators of surface braid groups
Yoshikata Kida, Saeko Yamagata
We prove that if g and n are integers at least two, then the abstract commensurator of the braid group with n strands on a closed orientable surface of genus g is naturally isomorp…
Parabolic isometries of CAT(0) spaces and CAT(0) dimensions
Koji Fujiwara, Takashi Shioya, Saeko Yamagata
We study discrete groups from the view point of a dimension gap in connection to CAT(0) geometry. Developing studies by Brady-Crisp and Bridson, we show that there exist finitely p…