activity
20242026
collaborators

10 papers

math.AG2026

Quasi--splitting versus log canonicity

Kenta Sato, Shunsuke Takagi, Shou Yoshikawa

In this paper, we investigate the relationship between quasi--splitting and log canonicity. We show that if a numerically -Gorenstein normal singularity is quasi-$F^…

math.AG2026

Quasi--singularities and singularities in birational geometry

Tatsuro Kawakami, Shunsuke Takagi, Shou Yoshikawa

We give an overview of the theory of quasi--singularities, focusing on their connection with singularities in birational geometry.

math.AG2026

An explicit formula for the Artin invariant of smooth K3 hypersurfaces

Teppei Takamatsu, Shou Yoshikawa

We characterize the Artin invariant of a smooth K3 hypersurface in terms of quasi--splitting. As an application, we obtain an explicit formula for this invariant.

math.AG2026

Perfectoid pure thresholds of lifts of rational double points

Teppei Takamatsu, Shou Yoshikawa

We study the perfectoid pure threshold with respect to , an invariant of singularities in mixed characteristic arising from perfectoid purity. In this paper, we compute…

math.AG2026

Non-quasi--split canonical affine fourfolds exist in every characteristic

Teppei Takamatsu, Shou Yoshikawa

We construct canonical -factorial Gorenstein affine fourfolds in every positive characteristic that are not quasi--split.

math.AC2026

Quasi--split height versus quasi--regular height for rational double points and graded rings

Teppei Takamatsu, Shou Yoshikawa

In this paper, we study a phenomenon concerning quasi--singularities: under suitable hypotheses, the finiteness of the quasi--split height () i…

math.AG2025

Quasi--splitting and smooth weak del Pezzo surfaces in mixed characteristic

Hirotaka Onuki, Teppei Takamatsu, Shou Yoshikawa

We introduce the notion of quasi--splitting in mixed characteristic and study Kodaira-type vanishing on quasi--splitting varieties. As an application, we prove a Kodaira-type…

math.AG2025

Fedder type criteria for quasi--splitting II

Tatsuro Kawakami, Teppei Takamatsu, Shou Yoshikawa

In this paper, we apply Fedder-type criteria for quasi--splitting to provide explicit computations of quasi--split heights for Calabi-Yau hypersurfaces, bielliptic surfaces,…

math.AG2025

Fedder-type criterion for quasi--splitting and quasi--regularity

Shou Yoshikawa

We study quasi--split and quasi--regular singularities, which generalize Yobuko's quasi--splitting. We establish Fedder type criteria that characterize these properties…

math.AG2024

Quasi-F-splittings in birational geometry III

Tatsuro Kawakami, Teppei Takamatsu, Hiromu Tanaka +3

We prove that -Gorenstein quasi--regular singularities are klt. To this end, we shall introduce quasi-test ideals.