Kiwamu Watanabe

collaborators

3 papers

math.AG2025

Characterization of products of projective spaces via nef complexity

Joshua Enwright, Stefano Filipazzi, Yoshinori Gongyo +4

We define the nef complexity of a projective variety $X$ . This invariant compares $dim X + I ¨ (X)$ with the sum of the coefficients of nef partitions of $- K_{X}$ . We prove that the nef…

math.AG2025

Smooth Fano varieties with pseudoindex equal to half of their dimension

Kiwamu Watanabe

Let $X$ be a complex smooth Fano variety of dimension $n$ . Assume that $X$ admits a birational contraction of an extremal ray. In this paper, we give a classification of such $X$ w…

math.AG2025

Quadratic Varieties of Small Codimension

Kiwamu Watanabe

Let $X \subset P^{n + c}$ be a nondegenerate smooth projective variety of dimension $n$ defined by quadratic equations. For such varieties, P. Ionescu and F. Russo proved th…