\input zb-basic
\input zb-ioport
\iteman{io-port 06121288}
\itemau{Scheiblechner, Peter}
\itemti{Castelnuovo-Mumford regularity and computing the de Rham cohomology of smooth projective varieties.}
\itemso{Found. Comput. Math. 12, No. 5, 541-571 (2012).}
\itemab
Summary: 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. By covering $X$ with sets of this type and using a \v{C}ech process, we obtain 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.
\itemrv{~}
\itemcc{}
\itemut{Castelnuovo-Mumford regularity; de Rham cohomology; algorithm; complexity; parallel polynomial time; smooth projective variety; Betti numbers; \v{C}ech cohomology; hypercohomology}
\itemli{doi:10.1007/s10208-012-9123-y}
\end