关于辛半平坦6-流形的自同构群

K3 surfaces with non-symplectic automorphisms of order three and Calabi-Yau orbifolds

Let S be a K3 surface that admits a non-symplectic automorphism $ρ$ of order 3. We divide $S\times \mathbb{P}^1$ by $ρ\timesψ$ where $ψ$ is an automorphism of order 3 of $\mathbb{P}^1$. There exists a threefold ramified cover of a partial crepant resolution of the quotient that is a Calabi-Yau orbifold. We compute the Euler characteristic of our examples and obtain values ranging from 30 to 219.

On the splitting of infinitesimal Poisson automorphisms around symplectic leaves

A geometric description of the first Poisson cohomology groups is given in the semilocal context, around (possibly singular) symplectic leaves. This result is based on the splitting theorems for infinitesimal automorphisms of coupling Poisson structures which describe the interaction between the tangential and transversal data of the characteristic distributions. As a consequence, we derive some criteria of vanishing of the first Poisson cohomology groups and apply the general splitting formulas to some particular classes of Poisson structures associated with singular symplectic foliations.

Uniqueness of optimal symplectic connections

Consider a holomorphic submersion between compact Kähler manifolds, such that each fibre admits a constant scalar curvature Kähler metric. When the fibres admit continuous automorphisms, a choice of fibrewise constant scalar curvature Kähler metric is not unique. An optimal symplectic connection is choice of fibrewise constant scalar curvature Kähler metric satisfying a geometric partial differential equation. The condition generalises the Hermite-Einstein condition for a holomorphic vector bundle, through the induced fibrewise Fubini-Study metric on the associated projectivisation. We prove v…

李群体的自同构与orbifold上的辛约简

Automorphisms of Lie groupoids and symplectic reduction on orbifolds

本文研究了李群体的自同构2-群BAut(X)以及其在orbifold上的辛约简，通过Kan纤维化理论建立了2-群作用与李群体的等价关系，并探讨了辛约简的性质和应用。

Matsushima-Lichnerowicz type theorems of Lie algebra of automorphisms of generalized Kähler manifolds of symplectic type

In Kähler geometry, Fujiki--Donaldson show that the scalar curvature arises as the moment map for Hamiltonian diffeomorphisms. In generalized Kähler geometry, one does not have suitable notions of Levi-Civita connection and curvature, however there still exists a precise framework for a moment map and the scalar curvature is defined as the moment map. Then a fundamental question is to understand the existence or non-existence of generalized Kähler structures with constant scalar curvature. In the paper, we study the Lie algebra of automorphisms of a generalized complex manifold. We assume that…

Automorphisms of the Weyl manifold

Assume that $M$ is a smooth manifold with a symplectic structure $ω$. Then Weyl manifolds on the symplectic manifold $M$ are Weyl algebra bundles endowed with suitable transition functions. From the geometrical point of view, Weyl manifolds can be regarded as geometrizations of star products attached to $(M,ω)$. In the present paper, we are concerned with the automorphisms of the Weyl manifold corresponding to Poincaré-Cartan class ($c_0$ is a $\check{\rm C}$ech cocycle corresponding to the symplectic structure $ω$.) $[c_0+\sum_{\ell=1}^\infty c_{\ell} ν^{2\ell}]\in \check{H}^2 (M)[[ν^2]]$. We…

Symplectic half-flat solvmanifolds

We classify solvable Lie groups admitting left invariant symplectic half-flat structure. When the Lie group has a compact quotient by a lattice, we show that these structures provide solutions of supersymmetric equations of type IIA.

Special symplectic six-manifolds

We classify nilmanifolds with an invariant symplectic half-flat structure. We solve the half-flat evolution equations in one example, writing down the resulting Ricci-flat metric. We study the geometry of the orbit space of 6-manifolds with an SU(3)-structure preserved by a U(1) action, giving characterizations in the symplectic half-flat and integrable case.

Group-valued momentum maps for actions of automorphism groups

The space of smooth sections of a symplectic fiber bundle carries a natural symplectic structure. We provide a general framework to determine the momentum map for the action of the group of bundle automorphism on this space. Since, in general, this action does not admit a classical momentum map, we introduce the more general class of group-valued momentum maps which is inspired by the Poisson Lie setting. In this approach, the group-valued momentum map assigns to every section of the symplectic fiber bundle a principal circle-bundle with connection. The power of this general framework is illus…

齐性辛半平坦 6-流形

Homogeneous symplectic half-flat 6-manifolds

本文研究具有辛半平坦 SU(3)-结构的齐性 6-流形，证明不存在紧致非平坦例子，并在 G 半单的假设下完成非紧致情形的分类，同时刻画了 Ricci 张量的 Hermite 性质。

双曲接触辛提升

Hyperbolic contact symplectic lifts

研究全纯接触流形的双曲性，通过Reeb流形构造具有大自同构群的接触双曲流形，并证明其与Kobayashi双曲辛商的关系。

某些李群上的左不变辛结构的分类

A classification of left-invariant symplectic structures on some Lie groups

本文提出了一种新的方法，用于对某些李群上的左不变辛结构进行分类，通过分析非退化2形式的模空间并应用于特定维数的李群。