本文描述了紧致流形$M$上的主丛的无穷小自同构的李代数$\aut(P)$的自然交换扩张,并讨论了它们对相应李群扩张的可积性.一个平凡的包$P = M \times K$的情况已经很有趣了。在这种情况下,我们表明,基本上所有的规范代数$C^\infty(M,\fk)$的中心扩展可以得到从三个基本类型的上循环与空间$\fz := C^\infty(M,V)$,$Ω^1(M,V)$和$Ω^1(M,V)/\dd C^\infty(M,V)$之一的值。这些上循环扩展到$\aut(P)$,并且,在假设$TM$是平凡的,我们还描述了空间$H^2({\cal V}(M),\fz)$分类这些扩展的扭曲。然后,我们表明,所有的基本类型有自然的推广到非平凡的丛,并解释在何种条件下,他们扩展到$\aut(P)$和集成到全球李群扩展。
英文摘要:
We describe natural abelian extensions of the Lie algebra $\aut(P)$ of infinitesimal automorphisms of a principal bundle over a compact manifold $M$ and discuss their integrability to corresponding Lie group extensions. Already the case of a trivial bundle $P = M \times K$ is quite interesting. In this case, we show that essentially all central extensions of the gauge algebra $C^\infty(M,\fk)$ can be obtained from three fundamental types of cocycles with values in one of the spaces $\fz := C^\infty(M,V)$, $Ω^1(M,V)$ and $Ω^1(M,V)/\dd C^\infty(M,V)$. These cocycles extend to $\aut(P)$, and, under the assumption that $TM$ is trivial, we also describe the space $H^2({\cal V}(M),\fz)$ classifying the twists of these extensions. We then show that all fundamental types have natural generalizations to non-trivial bundles and explain under which conditions they extend to $\aut(P)$ and integrate to global Lie group extensions.
Automorphisms of non-singular nilpotent Lie algebras
对于一个实的、非奇异的、2步幂零李代数$\mathfrak{n}$,群\Aut(\mathfrak{n})/ \Aut_0(\mathfrak{n})$, where $ \Aut_0(\mathfrak{n})$ is the group of automorphisms which act trivially on the center, is the direct product of a compact group with the 1-dimensional group of dilations. Maximality of some automorphisms groups of $ \mathfrak{n} $ follows and is related to how close is $ \mathfrak{n} $ to being of Heisenberg type. For example, at least when the dimension of the center is two, $ \dim \Aut(\mathfrak{n})$ is maximal if and only if $ \mathfrak{n} $ is type $ H$。与脂肪分布的连接进行了讨论。
Matsushima-Lichnerowicz type theorems of Lie algebra of automorphisms of generalized Kähler manifolds of symplectic type
在Kähler几何中,Fujiki-Donaldson证明了数量曲率是作为哈密顿量同态的矩映射而产生的。在广义Kähler几何中,人们没有合适的Levi-Civita连接和曲率的概念,但是仍然存在一个精确的矩映射框架,并且数量曲率被定义为矩映射。然后一个基本的问题是理解具有常数数量曲率的广义Kähler结构的存在性或不存在性。本文研究广义复流形的自同构的李代数。我们假设$H^{1}(M)=0$。证明了如果一个广义复流形上存在一个具有常数量曲率的辛型广义Kähler结构,则其自同构的李代数是约化李代数.这是Kähler几何中Matsushima和Lichnerowicz定理的推广。本文明确地计算了由$\Bbb C P^2$上的三次曲线给出的广义复结构的自同构的李代数。三次曲线分为九种情况(见图)。$1 -- 9$)。在三种情况下,如图。7,8和9,自同构的李代数不是约化的,并且在这三种情况下存在具有常数数量曲率的辛型广义Kähler结构。我们还讨论了从一个普通的Kähler流形$(X,ω)$与常数数量曲率曲率的变形,并表明,非平凡的广义Kähler结构的辛型常数数量曲率曲率出现的变形,如果$X$的自同构的李代数是平凡的。