Projective varieties of maximal sectional regularity

Autor: Markus Brodmann, Peter Schenzel, Euisung Park, Wanseok Lee
Rok vydání: 2017
Předmět:
Zdroj: Journal of Pure and Applied Algebra. 221:98-118
ISSN: 0022-4049
DOI: 10.1016/j.jpaa.2016.05.028
Popis: We study projective varieties $X \subset \mathbb{P}^r$ of dimension $n \geq 2$, of codimension $c \geq 3$ and of degree $d \geq c + 3$ that are of maximal sectional regularity, i.e. varieties for which the Castelnuovo-Mumford regularity $\reg (\mathcal{C})$ of a general linear curve section is equal to $d -c+1$, the maximal possible value (see \cite{GruLPe}). As one of the main results we classify all varieties of maximal sectional regularity. If $X$ is a variety of maximal sectional regularity, then either (a) it is a divisor on a rational normal $(n+1)$-fold scroll $Y \subset \mathbb{P}^{n+3}$ or else (b) there is an $n$-dimensional linear subspace $\mathbb{F} \subset \mathbb{P}^r$ such that $X \cap \mathbb{F} \subset \mathbb{F}$ is a hypersurface of degree $d-c+1$. Moreover, suppose that $n = 2$ or the characteristic of the ground field is zero. Then in case (b) we obtain a precise description of $X$ as a birational linear projection of a rational normal $n$-fold scroll.
This paper extends and generalizes some results of arXiv:1305.2355. More precisely, we do not restrict ourselves to surfaces any more. Instead we give a classification of projective varieties of maximal sectional regularity of arbitrary dimension and codimension > 2
Databáze: OpenAIRE
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