293 citations · 506 across the 40 of their papers we have counts for
43 papers
Counterexamples to Hardy--Littlewood maximal inequalities on solvable groups
Koji Fujiwara
We prove that the centered Hardy--Littlewood maximal operator is not of weak type for any in three solvable settings: the lamplighter group $(\mathbb{Z}/2\m…
Finite covers of a product of surfaces with bounded rank and arbitrarily large systole
Koji Fujiwara
We construct finite covers of a fixed product of two closed hyperbolic surfaces of genus two whose fundamental groups are generated by at most fifteen elements and whose injectivit…
Small growth rates of free groups
Koji Fujiwara, Sang-hyun Kim, Ryokichi Tanaka
We introduce the notion of a Magnus marking for a finite generating set of a group and prove a certain expansion property. Using this property, we determine the second and third sm…
A coarse-geometry characterization of cacti
Koji Fujiwara, Panos Papasoglu
We give a quasi-isometric characterization of cacti, which is similar to Manning's characterization of quasi-trees by the bottleneck property. We also give another quasi-isometric…
Asymptotic dimensions of the arc graphs and disk graphs
Koji Fujiwara, Saul Schleimer
We give quadratic upper bounds for the asymptotic dimensions of the arc graphs and disk graphs.
An example of a closed 5-manifold of nonpositive curvature that fibers over a circle
Koji Fujiwara
We exhibit a closed aspherical 5-manifold of nonpositive curvature that fibers over a circle whose fundamental group is hyperbolic relative to abelian subgroups such that the fiber…