Ken-ichi Yoshida

activity

20242026

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6 papers · 1 filter

math.AG2025

A variant of R{ö}hr's vanishing theorem with an application to the normal reduction number for normal surface singularities

Tomohiro Okuma, Kei-ichi Watanabe, Ken-ichi Yoshida

Let $A$ be an excellent two-dimensional normal local ring containing an algebraically closed field and let $X \to Spec (A)$ be a resolution of singularity. We prove a theor…

math.AG2025

Nearly Gorenstein rational surface singularities

Kyosuke Maeda, Tomohiro Okuma, Kei-ichi Watanabe +1

In this paper, we show that for any rational surface singularity $A$ , the canonical trace ideal $Tr_{A} (K_{A})$ is an integrally closed ideal, which is represented by the mini…

math.AC2025

Gorenstein Normal tangent cones of integrally closed ideals in two-dimensional normal singularities

Tomohiro Okuma, Kei-ichi Watanabe, Ken-ichi Yoshida

Let $(A, m)$ be a two-dimensional excellent normal Gorenstein local domain containing an algebraically closed filed. Let $I = H^{0} (X, O_{X} (- Z)) \subset A$ be an $\ma…

math.AC2025

Hilbert-Kunz multiplicity of quadrics via Ehrhart theory

Igor Pak, Boris Shapiro, Ilya Smirnov +1

We show that the Hilbert-Kunz multiplicity of the d-dimensional non-degenerate quadric hypersurface of characteristic p > 2 is a rational function of p composed from the Ehrhart po…

math.AC2025

Ulrich ideals on rational triple points of dimension two

Kyosuke Maeda, Ken-ichi Yoshida

In this paper, we prove the canonical trace ideal trace(omega_A) is an Ulrich ideal for any two-dimensional rational triple point A. Using this, we classify all Ulrich ideals on ra…

math.GT2025

Uniqueness of free 2-periodicities of links

Ken'ichi Yoshida

We show that if two links in the real projective 3-space $RP^{3}$ have isotopic preimages in the 3-sphere $S^{3}$ by the double covering map, then they are themselves isot…