Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 0704.0874

Higher ramification and varieties of secant divisors on the generic curve

Gavril Farkas
View original source ↗Read source document ↗Export metadata ↓

Abstract

For a smooth projective curve, the cycles of e-secant k-planes are among the most studied objects in classical enumerative geometry and there are well-known formulas due to Castelnuovo, Cayley and MacDonald concerning them. Despite various attempts, surprisingly little is known about the enumerative validity of such formulas. The aim of this paper is to completely clarify this problem in the case of the generic curve C of given genus. Using degeneration techniques and a few facts about the birational geometry of moduli spaces of stable pointed curves we determine precisely under which conditions the cycle of e-secant k-planes in non-empty and we compute its dimension. We also precisely determine the dimension of the variety of linear series on C carrying e-secant k-planes. In a different direction, in the last part of the paper we study the distribution of ramification points of the powers of a line bundle on C having prescribed ramification at a given point.

Explore related subjects

math.AG

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Gavril Farkas. 2014-11-20. Higher ramification and varieties of secant divisors on the generic curve. https://arxiv.org/abs/0704.0874

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

On the fundamental groups of subelliptic varieties

We show that the fundamental group of any smooth subelliptic variety is finite. Moreover, it is also proved that every finite group can be realized as the fundamental group of a smooth subelliptic variety. As a consequence, it follows that there exists a smooth subelliptic variety homotopy equivalent to the $n$-sphere if and only if $n>1$. This result can be considered as a negative answer to the algebraic version of Gromov's problem on the homotopy types of Oka manifolds.

math.AG↗
arXiv2026

Minimal energy local systems on curves

Let $Σ_{g,n}$ be an orientable topological surface of genus $g$ with $n$ punctures. When $g = 0$, Deroin and Tholozan studied the class of supra-maximal representations $π_1(Σ_{0,n})\to \mathrm{PSL}_2(\mathbb{R})$, and they showed that the supra-maximal representations form a compact component of a real relative character variety. We study a collection of rank $r$ local systems on $Σ_{g,n}$ which we call of minimal energy. These are generalizations of supra-maximal representations, and underlie polarizable complex variations of Hodge structure for any choice of complex structure on $Σ_{g,n}$. Like the supra-maximal representations, the minimal energy local systems form compact components of relative character varieties of real forms of $\mathrm{GL}_r(\mathbb{C})$. We show that when the local monodromy data around the punctures is chosen to be unitary and generic, and the relative character variety is nonempty, these minimal energy local systems always exist. When $g > 0$, we show that the minimal energy local systems come from unitary representations of $π_1(Σ_{g,n})$. If $g = 0$ we show that they do not always come from unitary representations, and we study their structure in general.

math.AG↗
arXiv2026

Hypergeometric local systems and parabolic bundles

Beukers and Heckman gave necessary and sufficient conditions for a hypergeometric function $_n F_{n-1}$ to be algebraic. We give a new proof of this theorem by passing through the Mehta-Seshadri correspondence. In particular, we explicitly write down the parabolic bundle corresponding to a unitary hypergeometric local system.

math.AG↗