Calculating cohomology groups of moduli spaces of curves via algebraic geometry
Canonical liftings of jacobians
Castelnuovo Curves and Unobstructed Deformations.
Chen–Ruan Cohomology of and
In this work we compute the Chen–Ruan cohomology of the moduli spaces of smooth and stable -pointed curves of genus . In the first part of the paper we study and describe stack theoretically the twisted sectors of and . In the second part, we study the orbifold intersection theory of . We suggest a definition for an orbifold tautological ring in genus , which is a subring of both the Chen–Ruan cohomology and of the stringy Chow ring.
Codimension 1 subvarieties and real gonality of real curves
Let be the moduli space of smooth complex projective curves of genus . Here we prove that the subset of formed by all curves for which some Brill-Noether locus has dimension larger than the expected one has codimension at least two in . As an application we show that if is defined over , then there exists a low degree pencil defined over .
Cohomology of desingularization of moduli space of vector bundles
Cohomology of moduli spaces of stable curves.
Combinatorics of Mumford-Morita-Miller classes in low genus.
Compactification de l’espace des modules des variétés abéliennes principalement polarisées
Les variétés abéliennes principalement polarisées admettent un espace des modules grossier qu’on sait compactifier de plusieurs façons (compactification de Satake, compactifications toroïdales). Cependant, le problème s’est posé de construire une compactification “modulaire”en termes d’objets géométriques qui permettent de décrire les points du bord. On souhaite aussi compactifier l’application de Torelli qui à chaque courbe algébrique, projective et lisse, associe sa jacobienne. L’exposé présente...
Compactification du module des courbes
Compactification of the space of vector bundles on a singular curve.
Compactifications of moduli spaces of (semi)stable bundles on singular curves: two points of view.
Moduli spaces of vector bundles on families of non-singular curves are usually compactified by considering (slope)semistable bundles on stable curves. Alternatively, one could consider Hilbert-stable curves in Grassmannians. We study some properties of the latter and compare them with similar properties of curves coming from the former compactification. This leads to a new interpretation of the moduli space of (semi)stable torsion-free sheaves on a fixed nodal curve. One can present it as a quotient...
Comparison theorems for Gromov–Witten invariants of smooth pairs and of degenerations
We consider four approaches to relative Gromov–Witten theory and Gromov–Witten theory of degenerations: J. Li’s original approach, B. Kim’s logarithmic expansions, Abramovich–Fantechi’s orbifold expansions, and a logarithmic theory without expansions due to Gross–Siebert and Abramovich–Chen. We exhibit morphisms relating these moduli spaces and prove that their virtual fundamental classes are compatible by pushforward through these morphisms. This implies that the Gromov–Witten invariants associated...
Components of the Hilbert Scheme of Smooth space curves with the expected number of moduli.
Components with the expected codimension in the moduli scheme of stable spin curves
Here we study the Brill-Noether theory of “extremal” Cornalba’s theta-characteristics on stable curves C of genus g, where “extremal” means that they are line bundles on a quasi-stable model of C with #(Sing(C)) exceptional components
Conjecture de Bloch et nombres de Milnor
Nous déduisons de la formule du conducteur, conjecturée par S. Bloch, celle de P. Deligne exprimant, dans le cas d'une singularité isolée, la dimension totale des cycles évanescents en fonction du nombre de Milnor. En particulier, la formule de Deligne est établie en dimension relative un; en appendice, on généralise cet énoncé au cas d'un lieu singulier propre.
Conjecture de Franchetta forte.
Construction of families of curves from finite length graded modules.
Coupling of universal monodromy representations of Galois-Teichmüller modular groups.
Courbes de genre géométrique borné sur une surface de type général