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Singular hermitian metrics on holomorphic vector bundles  [PDF]
Hossein Raufi
Mathematics , 2012,
Abstract: We introduce and study a notion of singular hermitian metrics on holomorphic vector bundles, following Berndtsson and P{\u{a}}un. We define what it means for such a metric to be curved in the sense of Griffiths and investigate the assumptions needed in order to locally define the cuvature $\Theta^h$ as a matrix of currents. We then proceed to show that such metrics can be regularised in such a way that the corresponding curvature tensors converge weakly to $\Theta^h$. Finally we define what it means for $h$ to be strictly negatively curved in the sense of Nakano and show that it is possible to regularise such metrics with a sequence of smooth, strictly Nakano negative metrics.
Canonical singular hermitian metrics on relative logcanonical bundles  [PDF]
Hajime Tsuji
Mathematics , 2010,
Abstract: This supersedes 0704.0566. We prove the invariance of logarithmic plurigenera for a projective family of KLT pairs and the adjoint line bundle of KLT line bundles. The proof uses the canonical singular hermitian metrics on relative logcanonical bundles.
On the minimality of canonically attached singular Hermitian metrics on certain nef line bundles  [PDF]
Takayuki Koike
Mathematics , 2014, DOI: 10.1215/21562261-3089091
Abstract: We apply Ueda theory to a study of singular Hermitian metrics of a (strictly) nef line bundle $L$. Especially we study minimal singular metrics of $L$, metrics of $L$ with the mildest singularities among singular Hermitian metrics of $L$ whose local weights are plurisubharmonic. In some situations, we determine a minimal singular metric of $L$. As an application, we give new examples of (strictly) nef line bundles which admit no smooth Hermitian metric with semi-positive curvature.
Stability and Hermitian-Einstein metrics for vector bundles on framed manifolds  [PDF]
Matthias Stemmler
Mathematics , 2012, DOI: 10.1142/S0129167X12500917
Abstract: We adapt the notions of stability of holomorphic vector bundles in the sense of Mumford-Takemoto and Hermitian-Einstein metrics in holomorphic vector bundles for canonically polarized framed manifolds, i.e. compact complex manifolds X together with a smooth divisor D such that K_X \otimes [D] is ample. It turns out that the degree of a torsion-free coherent sheaf on X with respect to the polarization K_X \otimes [D] coincides with the degree with respect to the complete K\"ahler-Einstein metric g_{X \setminus D} on X \setminus D. For stable holomorphic vector bundles, we prove the existence of a Hermitian-Einstein metric with respect to g_{X \setminus D} and also the uniqueness in an adapted sense.
Canonical singular hermitian metrics on relative canonical bundles  [PDF]
Hajime Tsuji
Mathematics , 2007,
Abstract: We introduce a new class of canonical AZD's (called the supercanonical AZD's) on the canonical bundles of smooth projective varieties with pseudoeffective canonical classes. We study the variation of the supercanonical AZD $\hat{h}_{can}$ under projective deformations and give a new proof of the invariance of plurigenera.
$L^2$-extension theorems for jet sections of nef holomorphic vector bundles on compact K?hler manifolds and rational homogeneous manifolds, I  [PDF]
Qilin Yang
Mathematics , 2014,
Abstract: In this paper we study holomorphic vector bundles with singular Hermitian metrics whose curvature are Hermitian matrix currents. We obtain an extension theorem for holomorphic jet sections of nef holomorphic vector bundle on compact K\"ahler manifolds. Using it we prove that Fano manifolds with strong Griffiths nef tangent bundles are rational homogeneous spaces.
Affine Hermitian-Einstein Metrics  [PDF]
John Loftin
Mathematics , 2007,
Abstract: We develop a theory of stable bundles and affine Hermitian-Einstein metrics for flat vector bundles over a special affine manifold (a manifold admitting an atlas whose gluing maps are all locally constant volume-preserving affine maps). Our paper presents a parallel to Donaldson-Uhlenbeck-Yau's proof of the existence of Hermitian-Einstein metrics on K\"ahler manifolds, and the extension of this theorem by Li-Yau to the non-K\"ahler complex case of Gauduchon metrics. Our definition of stability involves only flat vector subbundles (and not singular subsheaves), and so is simpler than the complex case in some places.
Singular connections, WZNW action, and moduli of parabolic bundles on the sphere  [PDF]
Claudio Meneses,Leon A. Takhtajan
Mathematics , 2014,
Abstract: The moduli space of stable parabolic vector bundles of parabolic degree 0 over the Riemann sphere is considered. The vector bundle analog of the Klein's Hauptmodul is defined and the regular locus, a subset of bundles with minimal Birkhoff-Grothendieck decomposition and generic Bruhat type of the constant term at $\infty$, is introduced. For the restriction of the natural Kaehler metric to the regular locus a potential is constructed as the value of the regularized WZNW functional evaluated on singular Hermitian metrics in the corresponding vector bundles. It is shown that this potential is an antiderivative of a (1,0)-form on the regular locus, associated with a solution of the Riemann-Hilbert problem.
Arithmetic characteristic classes of automorphic vector bundles  [PDF]
J. I. Burgos Gil,J. Kramer,U. Kuehn
Mathematics , 2005,
Abstract: We develop a theory of arithmetic characteristic classes of (fully decomposed) automorphic vector bundles equipped with an invariant hermitian metric. These characteristic classes have values in an arithmetic Chow ring constructed by means of differential forms with certain log-log type singularities. We first study the cohomological properties of log-log differential forms, prove a Poincar\'e lemma for them and construct the corresponding arithmetic Chow groups. Then we introduce the notion of log-singular hermitian vector bundles, which is a variant of the good hermitian vector bundles introduced by Mumford, and we develop the theory of arithmetic characteristic classes. Finally we prove that the hermitian metrics of automorphic vector bundles considered by Mumford are not only good but also log-singular. The theory presented here provides the theoretical background which is required in the formulation of the conjectures of Maillot-Roessler in the semi-abelian case and which is needed to extend Kudla's program about arithmetic intersections on Shimura varieties to the non compact case.
The Nakano vanishing theorem and a vanishing theorem of Demailly-Nadel type for holomorphic vector bundles  [PDF]
Hossein Raufi
Mathematics , 2012,
Abstract: We prove the classical Nakano vanishing theorem with H\"ormander $L^2$-estimates on a compact K\"ahler manifold using Siu's so called $\partial\dbar$-Bochner-Kodaira method, thereby avoiding the K\"ahler identities completely. We then introduce singular hermitian metrics on holomorphic vector bundles, and proceed to prove a vanishing theorem of Demailly-Nadel type for these in the special case where the base manifold is a Riemann surface.
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