The exceptional holonomy groups are G2 in 7 dimensions, and Spin(7) in 8 dimensions. In a previous paper (Invent. math. 123 (1996), 507-552) the author constructed the first examples of compact 8-manifolds with holonomy Spin(7), by resolving orbifolds T^8/G, where T^8 is the 8-torus and G a finite group of automorphisms of T^8.
This paper describes a different construction of compact 8-manifolds with holonomy Spin(7). We start with a Calabi-Yau 4-orbifold Y with isolated singularities, and an isometric, antiholomorphic involution σof Y fixing only the singular points. Let Z=Y/<σ>. Then Z is an orbifold with isolated singularities, and a natural Spin(7)-structure. We resolve the singular points of Z to get a compact 8-manifold M, and show that M has holonomy Spin(7).
Taking Y to be a hypersurface in a complex weighted projective space, we construct new examples of compact 8-manifolds with holonomy Spin(7), and calculate their Betti numbers b^k. The fourth Betti number b^4 tends to be rather large, as high as 11,662 in one example.
We study mirror symmetry of type II strings on manifolds with the exceptional holonomy groups $G_2$ and Spin(7). Our central result is a construction of mirrors of Spin(7) manifolds realized as generalized connected sums. In parallel to twisted connected sum $G_2$ manifolds, mirrors of such Spin(7) manifolds can be found by applying mirror symmetry to the pair of non-compact manifolds they are glued from. To provide non-trivial checks for such geometric mirror constructions, we give a CFT analysis of mirror maps for Joyce orbifolds in several new instances for both the Spin(7) and the $G_2$ ca…
本文的目的是证明Finsler流形的完整性可以与黎曼流形的完整性有很大的不同。证明了维数大于2的非零常曲率正定非黎曼Finsler流形的和乐群不可能是紧李群.因此这个和乐群不会作为任何黎曼流形的和乐群出现。另外，我们给出了Heisenberg群上左不变Finsler度量的一个例子，使得它的和乐群不是（有限维）李群.这些结果肯定地回答了S. S. Chern和Z. Shen：“有没有一个Finsler流形的和乐群不是任何黎曼流形的和乐群？"
According to the Markus conjecture, closed flat affine manifolds with parallel volume should be complete. We show it is the case for three-manifolds when the holonomy centralizes an affine transformation preserving the volume. It is notably the case when the holonomy group has non trivial center or when the automorphism group is non discrete.
In this paper we discuss some examples and general properties of holonomy groups of $\nabla^φ$ introduced by Wylie and the author, the connection corresponding to the $N=1$ Bakry-Émery Ricci curvature, and also Wylie's $\bar{\mathrm{sec}}_f$. In particular we classify all possible holonomy groups in dimension 2 and also provide two infinite families: $SL_n(\mathbb{R})$ and $SO^+(p,q)$.
Constructing compact manifolds with exceptional holonomy
例外的和乐群是7维的G2和8维的Spin（7）。具有这些和乐群的黎曼流形是Ricci平坦的。这是一篇综述性的论文，主要讨论了具有完整性G2和Spin（7）的紧致7-和8-流形的构造。最简单的构造方法是使用复几何和卡-丘分析的技巧来解决环面orbifold T^7/G或T^8/G的奇点，其中G是一个在T^7或T^8上保持平坦G2或Spin（7）-结构的有限群。也有更复杂的结构，开始于一个卡-丘流形或orbifold。本文中的所有材料在作者的书中有更详细的介绍，“Compact manifold with special holonomy”，牛津大学出版社，2000年。
Our aim is to support the choice of two remarkable connections with torsion in a 3-Sasakian manifold, proving that, in contrast to the Levi-Civita connection, the holonomy group in the homogeneous cases reduces to a proper subgroup of the special orthogonal group, of dimension considerably smaller. We realize the computations of the holonomies in a unified way, by using as a main algebraic tool a nonassociative structure, that one of symplectic triple system.
In this article, we introduce and study the notion of a complete special holonomy manifold $(X,ω)$ which is given by a global perturbation potential function, i.e., there is a function $f$ on $X$ such that $ω'=ω-\mathcal{L}_{\nabla f}ω$ is sufficiently small in $L^{\infty}$-norm. We establish some vanishing theorems on the $L^{2}$ harmonic forms under some conditions on the global perturbation potential function.
In this paper we establish a strong multiplicity one type property for the length-holonomy spectrum for the three dimensional compact hyperbolic spaces. We use the analytic properties of Selberg-Gangolli-Wakayama zeta functions associated to compact hyperbolic spaces.
This is a survey paper. We explain the known constructions for two geometrically different classes of examples of compact Riemannian 7-manifolds with holonomy G2. One method uses resolutions of singularities of appropriately chosen 7-dimensional orbifolds, with the help of asymptotically locally Euclidean spaces. Another method uses the gluing of two asymptotically cylindrical pieces and requires a certain matching condition for their cross-sections `at infinity'.
