Berechnung der Homologiegruppen singularitätenfreier algebraischer Hyperflächen und Konstruktion von Repräsentanten ihrer Erzeugenden
Big groups of automorphisms of some Klein surfaces.
Sea Xp una superficie de Klein compacta con borde de gen algebraico p ≥ 2. Se sabe que si G es un grupo de automorfismos de Xp entonces |G| ≤ 12(p- 1). Se dice que G es un grupo grande de gen p si |G| > 4(p -1). En el presente artículo se halla una familia de enteros p para los que el único grupo grande de gen p son los grupos diédricos. Esto significa que, en términos del gen real introducido por C. L. May, para tales valores de p no existen grupos grandes de gen real p.
Bilinear forms and extremal Kähler vector fields associated with Kähler classes.
Birational automorphisms of higher-dimensional algebraic varieties.
Birational invariants of algebraic varieties.
Birational isomorphisms of four-dimensional quintics.
Birational Morphisms Factorizable by two Monoidal Transformations.
Birational positivity in dimension
In this paper we prove that for a nonsingular projective variety of dimension at most 4 and with non-negative Kodaira dimension, the Kodaira dimension of coherent subsheaves of is bounded from above by the Kodaira dimension of the variety. This implies the finiteness of the fundamental group for such an provided that has vanishing Kodaira dimension and non-trivial holomorphic Euler characteristic.
Birational Properties of Moduli spaces of stable locally free rank-2 sheaves on algebraic surfaces.
Bogomolov instability of higher rank sheaves on surfaces in characteristic p.
Boundedness for codimension two submanifolds of quadrics.
It is proved that there are only finitely many families of codimension two subvarieties not of general type in Q6.
Boundedness for threefolds in P6 containing a smooth ruled surface as hyperplane section.
Let X ⊂ P6 be a smooth irreducible projective threefold, and d its degree. In this paper we prove that there exists a constant β such that for all X containing a smooth ruled surface as hyperplane section and not contained in a fourfold of degree less than or equal to 15, d ≤ β. Under some more restrictive hypothesis we prove an analogous result for threefolds containing a smooth ruled surface as hyperplane section and contained in a fourfold of degree less than or equal to 15.
Bounding automorphism groups.
Bounds for stable bundles and degrees of Weierstrass schemes.
Bounds for the number of connected components and the first Betti number mod two of a real algebraic surface
Bounds for the number of moduli for irregular varieties of general type.
Bounds on the denominators in the canonical bundle formula
In this work we study the moduli part in the canonical bundle formula of an lc-trivial fibration whose general fibre is a rational curve. If is the Cartier index of the fibre, it was expected that would provide a bound on the denominators of the moduli part. Here we prove that such a bound cannot even be polynomial in , we provide a bound and an example where the smallest integer that clears the denominators of the moduli part is . Moreover we prove that even locally the denominators depend...
Bounds on the number of non-rational subfields of a function field.
Brill–Noether loci for divisors on irregular varieties
We take up the study of the Brill-Noether loci , where is a smooth projective variety of dimension , , and is an integer. By studying the infinitesimal structure of these loci and the Petri map (defined in analogy with the case of curves), we obtain lower bounds for , where is a divisor that moves linearly on a smooth projective variety of maximal Albanese dimension. In this way we sharpen the results of [Xi] and we generalize them to dimension . In the -dimensional case we prove an...
Bubble tree compactification of moduli spaces of vector bundles on surfaces
We announce some results on compactifying moduli spaces of rank 2 vector bundles on surfaces by spaces of vector bundles on trees of surfaces. This is thought as an algebraic counterpart of the so-called bubbling of vector bundles and connections in differential geometry. The new moduli spaces are algebraic spaces arising as quotients by group actions according to a result of Kollár. As an example, the compactification of the space of stable rank 2 vector bundles with Chern classes c 1 = 0, c 1...