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A Nadel vanishing theorem for metrics with minimal singularities on big line bundles  [PDF]
Shin-ichi Matsumura
Mathematics , 2013,
Abstract: The purpose of this paper is to establish a Nadel vanishing theorem for big line bundles with multiplier ideal sheaves of singular metrics admitting an analytic Zariski decomposition (such as, metrics with minimal singularities and Siu's metrics). For this purpose, we apply the theory of harmonic integrals and generalize Enoki's proof of Koll'ar's injectivity theorem. Moreover we investigate the asymptotic behavior of harmonic forms with respect to a family of regularized metrics.
Metrics with cone singularities along normal crossing divisors and holomorphic tensor fields  [PDF]
Frédéric Campana,Henri Guenancia,Mihai P?un
Mathematics , 2011,
Abstract: We prove the existence of non-positively curved K\"ahler-Einstein metrics with cone singularities along a given simple normal crossing divisor on a compact K\"ahler manifold, under a technical condition on the cone angles, and we also discuss the case of positively-curved K\"ahler-Einstein metrics with cone singularities. As an application we extend to this setting classical results of Lichnerowicz and Kobayashi on the parallelism and vanishing of appropriate holomorphic tensor fields.
An injectivity theorem with multiplier ideal sheaves of singular metrics with transcendental singularities  [PDF]
Shin-ichi Matsumura
Mathematics , 2013,
Abstract: The purpose of this paper is to establish an injectivity theorem with multiplier ideal sheaves of singular metrics. This result is a generalization of various injectivity and vanishing theorems. To treat transcendental singularities, after regularizing a given singular metric, we study the asymptotic behavior of the harmonic forms with respect to a family of the regularized metrics. Moreover we give a method to obtain $L^2$-estimates of solutions of the $\overline{\partial}$-equation, by using the $\rm{\check{C}}$ech complex. As an application, we obtain a Nadel type vanishing theorem.
Quasi-Hodge Metrics and Canonical Singularities  [PDF]
Chin-Lung Wang
Mathematics , 2002,
Abstract: We study one parameter degenerations of complex projective manifolds by introducing certain type of Hodge metrics coming from the pluricanonical forms. We show that degenerations with at most canonical singularities are all in the finite distance boundary of moduli spaces. We also propose the converse to be true in the sense that finite distance degenerations admit birational models which have at most canonical singularities in the degenerate fiber. We verify this for curves and show that the Calabi-Yau case follows from the minimal model conjecture.
Vanishing cycles and singularities of meromorphic functions  [PDF]
Dirk Siersma,Mihai Tibar
Mathematics , 1999,
Abstract: We study vanishing cycles of meromorphic functions. This gives a new and unitary point of view, extending the study of the topology of holomorphic germs -- as initiated by Milnor in the sixties -- and of the global topology of polynomial functions, which has been advanced more recently. We define singularities along the poles with respect to a certain (weak) stratification and prove local and global bouquet structure in case of isolated singularities. In general, splitting of vanishing homology at singular points and global Picard-Lefschetz phenomena occur.
Einstein metrics and complex singularities  [PDF]
David M. J. Calderbank,Michael A. Singer
Mathematics , 2002, DOI: 10.1007/s00222-003-0344-1
Abstract: This paper is concerned with the construction of special metrics on non-compact 4-manifolds which arise as resolutions of complex orbifold singularities. Our study is close in spirit to the construction of the hyperkaehler gravitational instantons, but we focus on a different class of singularities. We show that any resolution X of an isolated cyclic quotient singularity admits a complete scalar-flat Kaehler metric (which is hyperkaehler if and only if c_1(X)=0), and that if c_1(X)<0 then X also admits a complete (non-Kaehler) self-dual Einstein metric of negative scalar curvature. In particular, complete self-dual Einstein metrics are constructed on simply-connected non-compact 4-manifolds with arbitrary second Betti number. Deformations of these self-dual Einstein metrics are also constructed: they come in families parameterized, roughly speaking, by free functions of one real variable. All the metrics constructed here are toric (that is, the isometry group contains a 2-torus) and are essentially explicit. The key to the construction is the remarkable fact that toric self-dual Einstein metrics are given quite generally in terms of linear partial differential equations on the hyperbolic plane.
Heights and metrics with logarithmic singularities  [PDF]
Gerard Freixas i Montplet
Mathematics , 2007,
Abstract: We prove lower bound and finiteness properties for arakelovian heights with respect to pre-log-log hermitian ample line bundles. These heights were introduced by Burgos, Kramer and K\"uhn, in their extension of the arithmetic intersection theory of Gillet and Soul\'e, aimed to deal with hermitian vector bundles equipped with metrics admitting suitable logarithmic singularities. Our results generalize the corresponding properties for the heights of Bost-Gillet-Soul\'e, as well as the properties established by Faltings for heights of points attached to hermitian line bundles whose metrics have logarithmic singularities. We also discuss various geometric constructions where such pre-log-log hermitian ample line bundles naturally arise.
Lojasiewicz exponents and resolution of singularities  [PDF]
Carles Bivià-Ausina,Santiago Encinas
Mathematics , 2009, DOI: 10.1007/s00013-009-0032-5
Abstract: We show an effective method to compute the \L ojasiewicz exponent of an arbitrary sheaf of ideals of $\OO_X$, where $X$ is a non-singular scheme. This method is based on the algorithm of resolution of singularities.
Metrics With Vanishing Quantum Corrections  [PDF]
A. A. Coley,G. W. Gibbons,S. Hervik,C. N. Pope
Physics , 2008, DOI: 10.1088/0264-9381/25/14/145017
Abstract: We investigate solutions of the classical Einstein or supergravity equations that solve any set of quantum corrected Einstein equations in which the Einstein tensor plus a multiple of the metric is equated to a symmetric conserved tensor $T_{\mu \nu}$ constructed from sums of terms the involving contractions of the metric and powers of arbitrary covariant derivatives of the curvature tensor. A classical solution, such as an Einstein metric, is called {\it universal} if, when evaluated on that Einstein metric, $T_{\mu \nu}$ is a multiple of the metric. A Ricci flat classical solution is called {\it strongly universal} if, when evaluated on that Ricci flat metric, $T_{\mu \nu}$ vanishes. It is well known that pp-waves in four spacetime dimensions are strongly universal. We focus attention on a natural generalisation; Einstein metrics with holonomy ${\rm Sim} (n-2)$ in which all scalar invariants are zero or constant. In four dimensions we demonstrate that the generalised Ghanam-Thompson metric is weakly universal and that the Goldberg-Kerr metric is strongly universal; indeed, we show that universality extends to all 4-dimensional ${\rm Sim}(2)$ Einstein metrics. We also discuss generalizations to higher dimensions.
HCMU metrics with cusp singularities and conical singularities  [PDF]
Chen Qing,Wu Yingyi,Xu Bin
Mathematics , 2013,
Abstract: An HCMU metric is a conformal metric which has a finite number of singularities on a compact Riemann surface and satisfies the equation of the extremal K\"{a}hler metric. In this paper, we give a necessary and sufficient condition for the existence of a kind of HCMU metrics which has both cusp singularities and conical singularities.
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