Cycles, submanifolds, and structures on normal bundles

Quantization of conic Lagrangian submanifolds of cotangent bundles

Let $M$ be a manifold and $Λ$ a compact exact connected Lagrangian submanifold of $T^*M$. We can associate with $Λ$ a conic Lagrangian submanifold $Λ'$ of $T^*(M\times R)$. We prove that there exists a canonical sheaf $F$ on $M\times R$ whose microsupport is $Λ'$ outside the zero section. We deduce the already known results that the Maslov class of $Λ$ is $0$ and that the projection from $Λ$ to $M$ induces isomorphisms between the homotopy groups.

Calibrated Manifolds and Gauge Theory

By a theorem of Mclean, the deformation space of an associative submanifold Y of an integrable G_2 manifold (M,ϕ) can be identified with the kernel of a Dirac operator D:Ω^{0}(ν) -->Ω^{0}(ν) on the normal bundle νof Y. Here, we generalize this to the non-integrable case, and also show that the deformation space becomes smooth after perturbing it by natural parameters, which corresponds to moving Y through `pseudo-associative' submanifolds. Infinitesimally, this corresponds to twisting the Dirac operator D --> D_{A} with connections A of ν. Furthermore, the normal bundles of the associative sub…

An index obstruction to positive scalar curvature on fiber bundles over aspherical manifolds

We exhibit geometric situations, where higher indices of the spinor Dirac operator on a spin manifold $N$ are obstructions to positive scalar curvature on an ambient manifold $M$ that contains $N$ as a submanifold. In the main result of this note, we show that the Rosenberg index of $N$ is an obstruction to positive scalar curvature on $M$ if $N \hookrightarrow M \twoheadrightarrow B$ is a fiber bundle of spin manifolds with $B$ aspherical and $π_1(B)$ of finite asymptotic dimension. The proof is based on a new variant of the multi-partitioned manifold index theorem which might be of independe…

$\mathbb{C}^3$ 的 Engel CR 子流形

Engel CR submanifolds of $\mathbb{C}^3$

本文给出了3维流形上$\mathbb{S}^1$丛浸入或嵌入$\mathbb{C}^3$且复切定义Engel结构的充分条件，构造了首批复切为Engel的紧子流形实例，回答了Y. Eliashberg的问题。

Homotopy classes of proper maps out of vector bundles

In this paper we classify the homotopy classes of proper maps $E\rightarrow \mathbb R^k$, where $E$ is a vector bundle over a compact Hausdorff space. As a corollary we compute the homotopy classes of proper maps $\mathbb R^n\rightarrow \mathbb R^k$. We find a stability range of such maps. We conclude with some remarks on framed submanifolds of non-compact manifolds, the relationship with proper homotopy classes of maps and the Pontryagin-Thom construction.

高维空间中非同源的单位余正则包

Legendrian non-isotopic unit conormal bundles in high dimensions

本文研究了高维空间中非同源的Legendrian子流形，通过定义非经典不变量区分无法通过经典不变量区分的单位余正则包。