I am an Associate Professor in the Department of Mathematics at Niigata University. My research interests include Hamiltonian dynamics in Symplectic Geometry.
Ph.D. in Mathematical Sciences, 2017
The University of Tokyo
Master of Mathematical Sciences, 2014
The University of Tokyo
Bachelor of Science, 2012
Kyushu University
We continue the study of Farber’s topological complexity for monotone symplectic manifolds initiated in [Or25]. First, we show that a closed spherically monotone symplectic manifold whose fundamental group contains no subgroup isomorphic to $\mathbb{Z}\oplus\mathbb{Z}$ is automatically toroidally monotone, with the same monotonicity constant. As a consequence, every closed $4$-dimensional spherically monotone symplectic manifold whose Kodaira dimension is not $-\infty$ and whose fundamental group contains no $\mathbb{Z}\oplus\mathbb{Z}$ (for instance, is Gromov hyperbolic) has maximal topological complexity $\mathrm{TC}(M)=9$. This settles, under strictly weaker hypotheses, the dichotomy $\mathrm{TC}(M)=8$, $9$ left open there. Second, we compute the topological complexity and the Lusternik–Schnirelmann category of all blowups of $S^2$-bundles over closed orientable surfaces of genus $g\geq 2$: they satisfy $\mathrm{cat}(M)=4$ and $\mathrm{TC}(M)=7$. In particular, the hypothesis on the Kodaira dimension in the first result cannot be removed, and closed symplectic $4$-manifolds realize the pairs $(\mathrm{cat}(M),\mathrm{TC}(M))=(3,5)$, $(4,7)$, $(5,9)$ in the three regimes considered in this paper. Throughout, $\mathrm{TC}$ and $\mathrm{cat}$ are taken in the unreduced convention.