Koji Fujiwara

activity

19952026

most citedBounded cohomology of subgroups of mapping class groups

293 citations · 506 across the 40 of their papers we have counts for

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3 papers · 1 filter

math.CA2026

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 $(p, p)$ for any $1 \leq p < \infty$ in three solvable settings: the lamplighter group $(\mathbb{Z}/2\m…

math.GT2026

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…

math.GR2026

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…