Kac-Moody群、其旗流形及分类空间的上同调环的计算

本文介绍Kac-Moody群、其旗流形及分类空间的上同调计算的发展历史与现状,并给出一些值得进一步关注和研究的问题.     

球几何三维流形到透镜空间的映射度

本文讨论球几何三维流形M=S~3/G,即S~3在一群G自由作用下的轨道空间.所谓球几何是指S~3上被赋予的标准的度量,其等距变换群是SO(4),而上述G就是SO(4)的离散子群.主要结果是利用Z在ZG模上的投射预解以及群G的上同调和流形K(G,1)的上同调的关系,计算出流形M的系数为Z_m(m不必为素数)的上同调环,以及Bockstein同态H~n(M,Z_m)→H~(n+1)(M,Z_m).利用上述结果进而计算出任一球几何三维流形到三维透镜空间的映射的映射度,最后可以判断一类映射是否具有值为1的映射度.     

李群表示论和Schubert条件

本文将Grassmann流形上的Schubert子簇所满足的经典的Schubert条件推广到一般的复半单李群G的广义旗流形.利用复半单李群的表示理论,我们首先在李群的权空间上引入自然的Ehresman偏序.这一偏序可以导出李群的最高权表示的权系、Weyl群及其陪集空间上的Ehresman偏序.然后我们对一般的复表示定义了相应的射影空间,Grassmann流形和旗流形.这使得能够像经典的情形一样来分析广义旗流形的Schubert子簇满足的Schubert条件.在讨论中,我们还给出了李群G的Weyl群及其陪集空间中的Bruhat-Chevalley偏序的简单判别条件.我们的结果应用到例外群,给出了Fulton提出的关于例外群的Schubert分析的问题的部分回答.     

复Stiefel流形的商空间

本文研究了复Stiefel流形关于群S1的商空间的伦型,并且计算了该空间的上同调群.通过纤维化,为这些商空间的上同调找到一组典则的生成元.再利用推广的吴公式,讨论了这些生成元在Sqi下的行为.最后,作为应用,本文对S.Gitler和D.Handel的结果作了部分改进.     

复Stiefel流形的商空间

本文研究了复Stiefe1流形关于群S1的商空间的伦型,并且计算了该空间的上同调群.通过纤维化,为这些商空间的上同调找到一组典则的生成元.再利用推广的吴公式,讨论了这些生成元在Sqi下的行为.最后,作为应用,本文对S.Gitler和D.Handel的结果作了部分改进.     

旗流形的上同调环的自同态

本文应用李群理论,对紧单李群Ｇ,给出了旗流形 Ｇ／Ｔ的上同调环自同态的完全分类,并对典型群计算了相应自同态的Ｌｅｆｓｃｈｅｔｚ数．     

一般Hopf曲面上的一类全纯线丛的上同调维数的计算公式

研究了具有任意基本群的非主Hopf流形上的全纯线丛．我们利用推广了Douady序列，利用群作用的方法，具体给出了一类具有非交换基本群的Hopf曲面上全纯线丛上同调维数的计算公式。     

几何分析中运用Gromov方法的几个课题

近３０年来Ｇｒｏｍｏｖ对数学的多个领域，其中包括微分几何，拓扑，动力系统，群论和偏微分方程，作出了重要的贡献，本文讨论几何分析中与Ｇｒｏｍｏｖ引进的多种几何不变量有关的几个专题中主要包括Ｇｒｏｍｏｖ几乎平坦流形，极小体积空隙独测，填充黎曼流形，等周不等式，Ｇｒｏｍｏｖ字双曲群，非紧空间和具有界曲率奇异空间上的加权Ｌ＾ｐ上同调。     

Kac-Moody群的抛物子群的同构型（英文）

本文讨论了Kac-Moody群的抛物子群的同构型.所得结果可应用于Kac-Moody群和它们的分类空间的拓扑的研究.     

3-对称Finsler流形（英文）

3-对称Finsler流形是3-对称黎曼流形的推广.本文给出了3-对称Finsler流形的定义,并将3-对称Finsler流形用齐性空间的形式表示.同时,本文还给出了在齐性空间上存在3-对称Finsler度量的条件,并讨论了3-对称Finsler流形与3-对称黎曼流形的关系.最后,本文给出了自然约化的3-对称Finsler流形的旗曲率和曲率张量.     

Computation of the cohomology rings of Kac-Moody groups,their flag manifolds and classifying spaces

In this paper we introduce the history and present situation of the computation of the cohomology rings of Kac-Moody groups, their flag manifolds and classifying spaces, and give some problems and conjectures that deserve further study.     

Elliptic rational spaces whose cohomologies and homotopies are isomorphic

We give two simply connected elliptic 79-dimensional closed smooth manifolds whose rational homotopy types are different. But both their rational cohomology rings and rational homotopy Lie algebras are isomorphic.     

Almost nonnegative curvature operator and cohomology rings

We give a survey of results on the construction of and obstructions to metrics of almost nonnegative curvature operator on closed manifolds and results on the cohomology rings of closed, simply-connected manifolds with a lower curvature and upper diameter bound. The latter is motivated by a question of Grove whether these condition imply finiteness of rational homotopy types. This question has answers by F. Fang–X. Rong, B. Totaro and recently A. Dessai and the present author.     

Cohomological non-rigidity of generalized real Bott manifolds of height 2

We investigate the following problem: When do two generalized real Bott manifolds of height 2 have isomorphic cohomology rings with ?/2 coefficients and also when are they diffeomorphic? It turns out that in general cohomology rings with ?/2 coefficients do not distinguish those manifolds up to diffeomorphism. This gives a negative answer to the cohomological rigidity problem for real toric manifolds posed earlier by Y. Kamishima and the present author. We also prove that generalized real Bott manifolds of height 2 are diffeomorphic if they are homotopy equivalent.     

Exotic torus manifolds and equivariant smooth structures on quasitoric manifolds

In 2006 Masuda and Suh asked if two compact non-singular toric varieties having isomorphic cohomology rings are homeomorphic. In the first part of this paper we discuss this question for topological generalizations of toric varieties, so-called torus manifolds. For example we show that there are homotopy equivalent torus manifolds which are not homeomorphic. Moreover, we characterize those groups which appear as the fundamental groups of locally standard torus manifolds. In the second part we give a classification of quasitoric manifolds and certain six-dimensional torus manifolds up to equivariant diffeomorphism. In the third part we enumerate the number of conjugacy classes of tori in the diffeomorphism group of torus manifolds. For torus manifolds of dimension greater than six there are always infinitely many conjugacy classes. We give examples which show that this does not hold for six-dimensional torus manifolds.     

Duality in algebra and topology

We apply ideas from commutative algebra, and Morita theory to algebraic topology using ring spectra. This allows us to prove new duality results in algebra and topology, and to view (1) Poincaré duality for manifolds, (2) Gorenstein duality for commutative rings, (3) Benson–Carlson duality for cohomology rings of finite groups, (4) Poincaré duality for groups and (5) Gross–Hopkins duality in chromatic stable homotopy theory as examples of a single phenomenon.     

Wedge Operations and Doubling Operations of Real Toric Manifolds

This paper deals with two things.First,the cohomology of canonical extensions of real topological toric manifolds is computed when coefficient ring G is a commutative ring in which 2 is unit in G.Second,the author focuses on a specific canonical extensions called doublings and presents their various properties.They include existence of infinitely many real topological toric manifolds admitting complex structures,and a way to construct infinitely many real toric manifolds which have an odd torsion in their cohomology groups.Moreover,some questions about real topological toric manifolds related to Halperin's toral rank conjecture are presented.     

Invariants for proper metric spaces and open Riemannian manifolds

We introduce uniform structures of proper metric spaces and open Riemannian manifolds, characterize their (arc) components, present new invariants like e.g. Lipschitz and Gromov–Hausdorff cohomology, specialize to uniform triangulations of manifolds and prove that the presence of a spectral gap above zero is a bounded homotopy invariant.     

Homotopy of gauge groups over non-simply-connected five-dimensional manifolds

Both the gauge groups and 5-manifolds are important in physics and mathematics. In this paper,we combine them to study the homotopy aspects of gauge groups over 5-manifolds. For principal bundles over non-simply connected oriented closed 5-manifolds of a certain type, we prove various homotopy decompositions of their gauge groups according to different geometric structures on the manifolds, and give the partial solution to the classification of the gauge groups. As applications, we estimate the homotopy exponents of their gauge groups, and show periodicity results of the homotopy groups of gauge groups analogous to the Bott periodicity.Our treatments here are also very effective for rational gauge groups in the general context, and applicable for higher dimensional manifolds.     

Simply connected Voisin manifolds of dimension four

Voisin constructed a series of examples of simply connected compact Kähler manifolds of even dimension, which do not have the rational homotopy type of a complex projective manifold starting from dimension six. In this note, we prove that Voisin's examples of dimension four also do not have the rational homotopy type of a complex projective manifold. Oguiso constructed simply connected compact Kähler manifolds starting from dimension four, which cannot deform to a complex projective manifold under a small deformation. We also prove that Oguiso's examples do not have the rational homotopy type of a complex projective manifold.