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arXiv 0905.2212math.AGcs.SC
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光滑Projective Varieties的Castelnuovo-Mumford正则性及de Rham上同调的计算

Castelnuovo-Mumford Regularity and Computing the de Rham Cohomology of Smooth Projective Varieties

Peter Scheiblechner

摘要:

我们描述了一个计算光滑复射影簇$X$的拓扑Betti数的并行多项式时间算法。它是第一个单一的指数时间算法计算的Betti数的一个显着的一类复杂的品种的任意维。我们的主要理论结果是:$X$上的$p$ -形式层的Castelnuovo-Mumford正则性是由$p(em+1)D$限定的,其中$e$,$m$和$D$分别是$X$的所有不可约分支的最大余维数,维数和度.由此可见,对于$X$中一般超平面截面的并集$V$,$X\setminus V$的代数de Rham上同调可用沿$V$的极点为单指数阶的微分形式来描述.这产生了类似的描述的德拉姆上同调的$X$,这使得其有效的计算。此外,我们给出了一个并行的多项式时间算法来检验一个投影簇是否光滑。

英文摘要:

We describe a parallel polynomial time algorithm for computing the topological Betti numbers of a smooth complex projective variety $X$. It is the first single exponential time algorithm for computing the Betti numbers of a significant class of complex varieties of arbitrary dimension. Our main theoretical result is that the Castelnuovo-Mumford regularity of the sheaf of differential $p$-forms on $X$ is bounded by $p(em+1)D$, where $e$, $m$, and $D$ are the maximal codimension, dimension, and degree, respectively, of all irreducible components of $X$. It follows that, for a union $V$ of generic hyperplane sections in $X$, the algebraic de Rham cohomology of $X\setminus V$ is described by differential forms with poles along $V$ of single exponential order. This yields a similar description of the de Rham cohomology of $X$, which allows its efficient computation. Furthermore, we give a parallel polynomial time algorithm for testing whether a projective variety is smooth.

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