arXiv subjects

Ben Weinkove

Publications and source records attributed to Ben Weinkove.

65 records · Page 4Linked to original sources

arXiv2007

The Calabi-Yau equation on almost-Kahler four-manifolds

Let (M, ω) be a compact symplectic 4-manifold with a compatible almost complex structure J. The problem of finding a J-compatible symplectic form with prescribed volume form is an almost-Kähler analogue of Yau's theorem and is connected to a programme in symplectic topology proposed by Donaldson. We call the corresponding equation for the symplectic form the Calabi-Yau equation. Solutions are unique in their cohomology class. It is shown in this paper that a solution to this equation exists if the Nijenhuis tensor is small in a certain sense. Without this assumption, it is shown that the problem of existence can be reduced to obtaining a C^0 bound on a scalar potential function.

math.DG↗

arXiv2007

Taming symplectic forms and the Calabi-Yau equation

We study the Calabi-Yau equation on symplectic manifolds. We show that Donaldson's conjecture on estimates for this equation in terms of a taming symplectic form can be reduced to an integral estimate of a scalar potential function. Under a positive curvature condition, we show that the conjecture holds.

math.DG↗

arXiv2006

The Moser-Trudinger inequality on Kahler-Einstein manifolds

We prove the conjecture of Tian on the strong form of the Moser-Trudinger inequality for Kahler-Einstein manifolds with positive first Chern class, when there are no holomorphic vector fields, and, more generally, when the setting is invariant under a maximal compact subgroup of the automorphism group.

math.DG↗

arXiv2006

The Calabi flow with small initial energy

We show that on Kahler manifolds M with c_1(M)=0 the Calabi flow converges to a constant scalar curvature metric if the initial Calabi energy is sufficiently small. We prove a similar result on manifolds with c_1(M)<0 if the Kahler class is close to the canonical class.

math.DG↗

arXiv2006

On Donaldson's flow of surfaces in a hyperkahler four-manifold

We prove some basic properties of Donaldson's flow of surfaces in a hyperkahler 4-manifold. When the initial submanifold is symplectic with respect to one Kähler form and Lagrangian with respect to another, we show that certain kinds of singularities cannot form, and we prove a convergence result under a condition related to one considered by M.-T. Wang for the mean curvature flow.

math.DG↗

arXiv2006

On the J-flow in higher dimensions and the lower boundedness of the Mabuchi energy

The J-flow is a parabolic flow on Kahler manifolds. It was defined by Donaldson in the setting of moment maps and by Chen as the gradient flow of the J-functional appearing in his formula for the Mabuchi energy. It is shown here that under a certain condition on the initial data, the J-flow converges to a critical metric. This is a generalization to higher dimensions of the author's previous work on Kahler surfaces. A corollary of this is the lower boundedness of the Mabuchi energy on Kahler classes satisfying a certain inequality when the first Chern class of the manifold is negative.

math.DG↗

arXiv2004

Convergence of the J-flow on Kahler surfaces

Donaldson defined a parabolic flow on Kahler manifolds which arises from considering the action of a group of symplectomorphisms on the space of smooth maps between manifolds. One can define a moment map for this action, and then consider the gradient flow of the square of its norm. Chen discovered the same flow from a different viewpoint and called it the J-flow, since it corresponds to the gradient flow of his J-functional, which is related to Mabuchi's K-energy. In this paper, we show that in the case of Kahler surfaces with two Kahler forms satisfying a certain inequality, the J-flow converges to a zero of the moment map.

math.DG↗

arXiv2004

On the convergence and singularities of the J-flow with applications to the Mabuchi energy

The J-flow of S. K. Donaldson and X. X. Chen is a parabolic flow on Kahler manifolds with two Kahler metrics. It is the gradient flow of the J-functional which appears in Chen's formula for the Mabuchi energy. We find a positivity condition in terms of the two metrics which is both necessary and sufficient for the convergence of the J-flow to a critical metric. We use this result to show that on manifolds with ample canonical bundle, the Mabuchi energy is proper on all Kahler classes in an open neighborhood of the canonical class defined by a positivity condition. This improves previous results of Chen and of the second author. We discuss the implications of this for the problem of the existence of constant scalar curvature Kahler metrics. We also study the singularities of the J-flow and, under certain conditions (which always hold for dimension two) derive estimates away from a subvariety. In the case of Kahler surfaces we use these estimates to confirm, at least in a certain sense, a conjectural remark of Donaldson that if the J-flow does not converge then it should blow up over some curves of negative self-intersection.

math.DG↗

arXiv2003

A complex Frobenius theorem, multiplier ideal sheaves and Hermitian-Einstein metrics on stable bundles

This paper describes how, in the case of algebraic surfaces, the well-known theorem of Donaldson-Uhlenbeck-Yau can be proved in a framework of generalized 'multiplier ideal sheaves', following the ideas of Siu. The key concept is that the destabilizing sheaf satisfies a differential inclusion relation. This relation is used, together with a complex Frobenius theorem for locally finitely generated subsheaves, to imply coherence of the destabilizing subsheaf.

math.DG↗

arXiv2003

Singularity formation in the Yang-Mills flow

This paper studies rapidly forming singularities in the Yang-Mills flow. It is shown that a sequence of blow-ups near the singular point converges, modulo the gauge group, to a homothetically shrinking soliton with non-zero curvature. The proof uses Hamilton's monotonicity formula. Examples of homothetically shrinking solitons are given in the case of trivial bundles over R^n for dimensions 5 through 9.

math.DG↗

arXiv2002

Higher K-energy functionals and higher Futaki invariants

This note discusses the higher K-energy functionals which were defined by Bando and Mabuchi, and integrate higher Futaki invariants. Two new formulas for the higher K-energy functionals are given, and the second K-energy is shown to be related to Donaldson's Lagrangian applied to metrics on the tangent bundle.

math.DG↗