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We study the codimension two locus $H$ in $𝒜_{g}$ consisting of principally polarized abelian varieties whose theta divisor has a singularity that is not an ordinary double point. We compute the class $[H] \in C H^{2} (𝒜_{g})$ for every $g$ . For $g = 4$ , this turns out to be the locus of Jacobians with a vanishing theta-null. For $g = 5$ , via the Prym map we show that $H \subset 𝒜_{5}$ has two components, both unirational, which we describe completely. We then determine the slope of the effective cone of $\bar{𝒜_{5}}$ and show that the component $\bar{N_{0}^{'}}$ of the Andreotti-Mayer...

In questa nota si danno dei criteri per la stabilità di fasci di quartiche piane.

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Schottky-Jung Relations and Vectorbundles on Hyperelliptic Curves.

Sections des fibrés vectoriels sur une courbe

Semi-Stable Curves on Algebraic Surfaces and Logarithmic Pluricanonical Maps.

Semistable Sheaves on Projective Varieties and Their Restriction to Curves.

Siegel modular forms vanishing on the moduli space.

Singular moduli and supersingular moduli of Drinfeld modules.

Singular Moduli, Modular Polynomials, and the Index of the Closure of Z [j (...)] in Q (j(...)).

Singularities of theta divisors and the geometry of $𝒜_{5}$

Slopes of effective divisors on the moduli space of stable curves.

Smoothness, semi-stability and alterations

Some more examples of curves in P3 with stable normal bundle.

Some remarks on the Severi varieties of surfaces in $ℙ^{3}$ .

Some results on the existence of rank two special stable vector bundles.

Some stability properties of Teichmüller modular function fields with pro-l weight structures.

Spectral Pairs, Mixed Hodge Modules, and Series of Plane Curve Singularities.

Stability of pencils of plane quartic curves

Stability of some bundles over curves

Stability of the homology of the moduli spaces of Riemann surfaces with spin structure.

Stable $G_{2}$ bundles and algebraically completely integrable systems

Stable Reflexive Sheaves. II.

Currently displaying 1 – 20 of 32