Searcharxiv⌕ Search

arXiv subjects

Andrei Teleman

Publications and source records attributed to Andrei Teleman.

47 records · Page 3Linked to original sources

Symplectic stability, analytic stability in non-algebraic complex geometry

We give a systematic presentation of the stability theory in the non-algebraic Kaehlerian geometry. We introduce the concept of "energy complete Hamiltonian action". To an energy complete Hamiltonian action of a reductive group G on a complex manifold one can associate a G-equivariant maximal weight function and prove a Hilbert criterion for semistability. In other words, for such actions, the symplectic semistability and analytic semistability conditions are equivalent.

math.CV↗

Gauge theoretical Gromov-Witten invariants and virtual fundamental classes

This article is an expanded version of talks given by the authors in Oberwolfach, Bochum, and at the Fano Conference in Torino. Some new results (e. g. the material concerning flag varieties, Quot spaces over $¶^1$, and the generalized quiver representations) were included. The main goal is the construction of gauge theoretical Gromov-Witten type invariants of arbitrary genus associated with certain symplectic factorization problems with additional symmetry, and the computation of these invariants in terms of complex geometric objects. The main tool for describing moduli spaces associated with symplectic factorization problems is the "universal Kobayashi-Hitchin correspondence", which gives canonical isomorphisms ${\cal M}^*\to{\cal M}^{\rm st}$ between gauge theoretic moduli spaces of irreducible solutions of certain PDE's and complex geometric moduli spaces of stable framed holomorphic objects. We state a conjecture for the general situation: When the gauge theoretic problem is of Fredholm type, and the data for ${\cal M}^{\rm st}$ are algebraic, then ${\cal M}^{\rm st}$ admits a canonical perfect obstruction theory in the sense of Behrend-Fantechi, and the Kobayashi-Hitchin isomorphism ${\cal M}^*\to{\cal M}^{\rm st}$ identifies the gauge theoretic and the algebraic virtual fundamental classes. The conjecture was checked for the symplectic factorization problems which yield the toric varieties.

math.AG↗

Holomorphic vector bundles on non-algebraic surfaces

The existence problem for holomorphic structures on vector bundles over non-algebraic surfaces is in general still open. We solve this problem in the case of rank 2 vector bundles over K3 surfaces and in the case of vector bundles of arbitrary rank over all known surfaces of class VII. Our methods, which are based on Donaldson theory and deformation theory, can be used to solve the existence problem of holomorphic vector bundles on further classes of non-algebraic surfaces.

math.AG↗

Moduli spaces of PU(2)-monopoles (revised version)

We prove generic regularity and Uhlenbeck-type compactification theorems for the moduli spaces of PU(2)-monopoles. Generic regularity is NOT obtained in the usual way (by applying Sard theorem to a smooth parameterized moduli space), since the parameterized moduli space can be a priori singular. We explain why, using the standard order 0-perturbations, one cannot get the smoothness of the parameterized moduli space. (The same difficulty arises in the case of ASD-Spin^c moduli spaces, so the definition of the Spin^c-polynomial invariants should be revised.) We show that the singular locus of the parameterized moduli space is contained in a closed subspace which is (in a certain sense) of infinite codimension, and we apply Sard theorem to the complement of this subspace. Our approach to prove Uhlenbeck compactness follows closely the strategy developed in the instanton case by Donaldson and Kronheimer. Similar results, with different methods, were obtained by Feehan - Leness and Feehan.

math.DG↗

Non-abelian Seiberg-Witten theory and projectively stable pairs

We introduce the concept of Spin^G-structure in a SO-bundle, where $G\subset U(V)$ is a compact Lie group containing $-id_V$. We study and classify $Spin^G(4)$-structures on 4-manifolds, we introduce the G-Monopole equations associated with a $Spin^G$-structure. On Kaehler surfaces a Kobayashi-Hitchin correspondence can be proved for the corresponding moduli spaces. Using this complex geometric interpretation, we determine explicitely a moduli space of "PU(2)-Monopoles" on $¶^2$, we describe its Uhlenbeck compactification, as well as the Donaldson- and the abelian locus.

alg-geom↗

Master Spaces for stable pairs

We construct master spaces for oriented torsion free sheaves coupled with morphisms into a fixed reference sheaf. These spaces are projective varieties endowed with a natural $\C^*$-action. The fixed point set of this action contains the moduli space of semistable oriented torsion free sheaves and the quot scheme associated with the given data. In the case of curves with trivial reference sheaf, our master spaces compactify the moduli spaces constructed by Bertram, Daskalopoulos and Wentworth. In the 2-dimensional case with trivial rank 1 reference sheaf, master spaces provide algebraic analoga of compactified moduli spaces of twisted quaternionic monopoles.

alg-geom↗

Seiberg-Witten invariants for manifolds with $b_+=1$

In this paper we describe the Seiberg-Witten invariants, which have been introduced by Witten, for manifolds with $b_+=1$. In this case the invariants depend on a chamber structure, and there exists a universal wall crossing formula. We take into account the contribution of the 1-homology of the base-manifold. For every Kähler surface with $p_g=0$ and $q$=0, these invariants are non-trivial for all $Spin^c(4)$-structures of non-negative index.

alg-geom↗

Seiberg-Witten invariants for manifolds with $b_+=1$, and the universal wall crossing formula

In this paper we describe the Seiberg-Witten invariants, which have been introduced by Witten, for manifolds with $b_+=1$. In this case the invariants depend on a chamber structure, and there exists a universal wall crossing formula. For every Kähler surface with $p_g=0$ and $q$=0, these invariants are non-trivial for all $Spin^c(4)$-structures of non-negative index.

alg-geom↗

Seiberg-Witten Invariants and Rationality of Complex Surfaces

The purpose of this paper is: 1) to explain the Seiberg-Witten invariants, 2) to show that - on a Kähler surface - the solutions of the monopole equations can be interpreted as algebraic objects, namely effective divisors, 3) to give - as an application - a short selfcontained proof for the fact that rationality of complex surfaces is a ${\cal C}^{\infty}$-property.

alg-geom↗