Author

Koji Fujiwara

3 papers indexed here

We haven’t gathered this author’s papers yet. Follow them and we’ll fetch their work.

Not the right person? Other researchers publish under this name.

Preprint Oct 2026

Drift and joint minimal displacement for groups acting on hyperbolic spaces

We obtain a uniform lower bound for the drift of random walks on hyperbolic spaces in terms of joint minimal displacement. Our main theorem applies to weakly acylindrical actions on Gromov-hyperbolic spaces and is quantitative in all relevant constants. For discrete isometry groups of Hadamard manifolds with pinched ne...

Koji Fujiwara, Ryokichi Tanaka · 0 citations

Preprint Sep 2026

Finite covers of a product of surfaces with bounded rank and arbitrarily large systole

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 injectivity radii tend to infinity. The construction uses fibre products over finite groups. These covers are closed aspherical four-manifolds with un...

Koji Fujiwara · 0 citations

Preprint Oct 2026

Counterexamples to Hardy--Littlewood maximal inequalities on solvable groups

We prove that the centered Hardy--Littlewood maximal operator is not of weak type $(p,p)$ for any $1\le p<\infty$ in three solvable settings: the lamplighter group $(\mathbb{Z}/2\mathbb{Z})\wr\mathbb{Z}$ with the switch--walk--switch word metric, the Baumslag--Solitar groups $BS(1,n)$, $n\ge2$, with their digit word me...

Koji Fujiwara · 0 citations