Agusti Roig, Martintxo Saralegi-Aranguren
Let $Φ\colon \sbat \times M \to M$ be a smooth action of the unit circle $ \sbat$ on a manifold $M$. In this work, we compute the minimal model of $M$ in terms of the orbit space $B$ and the fixed point set $F\subset B$, as a dg-module over the Sullivan's minimal model of $B$.
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We establish an S^1-equivariant index theorem for Dirac operators on Z/k-manifolds. As an application, we generalize the Atiyah-Hirzebruch vanishing theorem for S^1-actions on closed spin manifolds to the case of Z/k-manifolds.
Lower bound on the number of fixed points for circle actions on 10-dimensional almost complex manifolds
本文研究了10维近复流形上圆作用固定点数的下界，证明至少存在6个固定点，并给出了达到该下限的例子。
Circle actions on 6-dimensional oriented manifolds with 4 fixed points
本文分类了6维紧致定向流形上恰含4个不动点的圆周作用的不动点数据，证明其只能对应两个6球面旋转的不相交并集或 $\mathbb{CP}^3$ 上的线性作用，并涵盖 Petrie 奇异作用。
We determine the homeomorphism (resp. diffeomorphism) types of those 2-connected 7-manifolds (resp. smooth 2-connected 7-manifolds) that admit regular circle actions (resp. smooth regular circle actions).
A classical result says that a free action of the circle $\Bbb{S}^1$ on a topological space $X$ is geometrically classified by the orbit space $B$ and by a cohomological class ${H}^{^{2}}{(B,\Bbb{Z})}$, the Euler class. When the action is not free we have a difficult open question: $Π$ : "Is the space $X$ determined by the orbit space $B$ and the Euler class?" The main result of this work is a step towards the understanding of the above question in the category of unfolded pseudomanifolds. We prove that the orbit space $B$ and the Euler class determine: * the intersection cohomology of $X$, * …
The main purpose this work is to study the minimal fixed point set of fiber-preserving maps for spaces which are fiber bundles over the circle and the fiber is the torus. Using the one-parameter fixed point theory is possible to describe these sets in terms of the fundamental group and the induced homomorphism.
Following the idea of Lusztig, Atiyah-Hirzebruch and Kosniowski, we note that the Dolbeault-type operators on compact, almost-complex manifolds are rigid. When the circle action has isolated fixed points, this rigidity result will produce many identities concerning the weights on the fixed points. In particular, it gives a criterion to detemine whether or not a symplectic circle action with isolated fixed points is Hamiltonian. As applications, we simplify the proofs of some known results related to symplectic circle actions, due to Godinho, Tolman-Weitsman and Pelayo-Tolman, and generalize so…
Kawakubo and Uchida showed that, if a closed oriented $4k$-dimensional manifold $M$ admits a semi-free circle action such that the dimension of the fixed point set is less than $2k$, then the signature of $M$ vanishes. In this note, by using $G$-signature theorem and the rigidity of the signature operator, we generalize this result to more general circle actions. Combining the same idea with the remarkable Witten-Taubes-Bott rigidity theorem, we explore more vanishing results on spin manifolds admitting such circle actions. Our results are closely related to some earlier results of Conner-Floy…
The language of Harvey-Lawson currents and sparks may be useful for the study of Hopkins-Singer Wu classes in geometric topology, via equivariant Tate $K$-theory of circle actions and distributional generalizations of classical zeta functions.
The classification of Seifert manifolds was given in terms of numeric data by Seifert in 1933, and then generalized by Orlik and Raymond in 1968 to circle actions on closed 3d manifolds. In this paper, we further generalize the classification to circle actions on 3d manifolds with boundaries by adding a numeric parameter and a union of cycle graphs. Then we describe the equivariant cohomology of 3d manifolds with circle actions in terms of ring, module and vector-space structures. We also compute equivariant Betti numbers and Poincaré series for these manifolds and discuss the equivariant form…
We show that the fundamental group of Symp(M,w) can be nontrivial for M that does not admit any symplectic circle action.
We show that almost complex circle actions with exactly three fixed points do not exist in dimension 8 and present an infinite series of 6-dimensional manifolds possessing an almost complex circle action with exactly two fixed points.
This paper contains several results concerning circle action on almost-complex and smooth manifolds. More precisely, we show that, for an almost-complex manifold $M^{2mn}$(resp. a smooth manifold $N^{4mn}$), if there exists a partition $λ=(λ_{1},...,λ_{u})$ of weight $m$ such that the Chern number $(c_{λ_{1}}... c_{λ_{u}})^{n}[M]$ (resp. Pontrjagin number $(p_{λ_{1}}... p_{λ_{u}})^{n}[N]$) is nonzero, then \emph{any} circle action on $M^{2mn}$ (resp. $N^{4mn}$) has at least $n+1$ fixed points. When an even-dimensional smooth manifold $N^{2n}$ admits a semi-free action with isolated fixed point…
Spin structures on complex projective spaces and circle actions
该研究针对复射影空间旋量结构的存在性问题，利用圆周作用给出了偶维复射影空间$\u2119ℂ^{2m}$不具有旋量结构的新证明，为相关拓扑结论提供了新的论证视角。
We investigate a PL topology question: which circle bundles can be triangulated over a given triangulation of the base? The question got a simple answer emphasizing the role of minimal triangulations encoded by local systems of circular permutations of vertices of the base simplices. The answer is based on an experimental fact: classical Huntington transitivity axiom for cyclic orders can be expressed as the universal binary Chern cocycle.
Classical work of Lee, Schultz, and Stolz relates the smooth transformation groups of exotic spheres to the stable homotopy groups of spheres. In this note, we apply recent progress on the latter to produce smooth circle and cyclic group actions on certain exotic spheres.
We show that Connes' B-operator on a cyclic differential graded k-module M is a model for the canonical circle action on the geometric realization of M. This implies that the negative cyclic homology and the periodic cyclic homology of a differential graded category can be identified with the homotopy fixed points and the Tate fixed points of the circle action on its Hochschild complex.
Free circle actions on certain simply connected $7-$manifolds
研究确定哪些非负整数k,l和同调7球面Σ使kS²×S⁵#lS³×S⁴#Σ具有自由光滑圆作用
Homotopy minimal periods for fiber maps on circle bundles over circle
研究纤维丛上纤维映射的同伦极小周期，给出了基和纤维均为$S^{1}$的纤维丛上同伦极小周期的完整描述。
We prove that if the circle group acts smooth and unitary on 2n-dimensional stably complex manifold with two isolated fixed points and it is not bound equivariantly, then n=1 or 3. Our proof relies on the rigid Hirzebruch genera.
Swan-Tate cohomology of meromorphic circle actions
该研究借助带自由圆周作用的流形配边提出对称性破缺的玩具模型，定义复定向E_∞环谱的Swan-Tate上同调并回顾H、K、MU情形下的λ-环结构。
In this paper, we prove that the orbit space B and the Euler class of an action of the circle S^1 on X determine both the equivariant intersection cohomology of the pseudomanifold X and its localization. We also construct a spectral sequence converging to the equivariant intersection cohomology of X whose third term is described in terms of the intersection cohomology of B.
In the paper we describe obstructions for the existence of symplectic and Hamiltonian symplectic circle actions on closed compact manifolds in terms of Hirzebruch genera and relations between differential and homotopic invariants of such manifolds.
This paper has been withdrawn.
Free circle actions on $(n-1)$-connected $(2n+1)$-manifolds
该研究在n≡5,7模8的条件下，对容许自由圆周作用的同调无挠(n-1)-连通(2n+1)-流形完成了几乎微分同胚意义下的分类。
Free Circle Actions on the Product of Three Spheres
本文将三个球面乘积上自由S^0-作用的轨道空间分类推广到自由S^1-作用，并建立Borsuk-Ulam型定理。
Circle actions on six dimensional oriented manifolds with isolated fixed points
本文研究了六维定向流形上圆作用的固定点数据，通过等变连通和操作将其简化为无固定点作用，揭示了固定点数据的可消去性。
Weights of circle actions on oriented manifolds with isolated fixed points
本文针对圆群在具有孤立不动点的紧致有向流形上的作用，证明了不动点处权重成对出现的断言，且无需假设迷向子流形可定向，推广了已知结果。
Assume $(M, ω)$ is a connected, compact 6 dimensional symplectic manifold equipped with a semi-free Hamiltonian circle action, such that the fixed point set consists of isolated points or compact orientable surfaces. We restrict attention to the case $\dim$ $H^2(M)<3$. We give a complete list of the possible manifolds, determine their equivariant cohomology ring and equivariant Chern classes. Some of these manifolds are classified up to diffeomorphism. We also show the existence for a few cases.
Minimal triangulations of circle bundles
本文针对经典单纯复形情形的圆丛三角剖分问题，给出一类无穷多已三角剖分球面的精确解答，并提出一般情形下三角剖分存在的充分判据，可直接推导部分极小性结果。
Exotic almost complex circle actions on 6-manifolds
本文利用Kustarev手术构造解决了Jang对6维近复圆作用分类中一个未知情形的存在性问题，证明底流形为S^4×S^2且该作用不等变于线性作用，从而给出新的奇异S^1-作用。
This paper confirms the following suggestion of Kontsevich. In the appropriate derived sense, an action of the framed little disks operad and a trivialization of the circle action is the same information as an action of the Deligne-Mumford-Knudsen operad. This improves an earlier result of the author and Bruno Vallette.
A Bott tower is the total space of a tower of fibre bundles with base CP^1 and fibres CP^1. Every Bott tower of height n is a smooth projective toric variety whose moment polytope is combinatorially equivalent to an n-cube. A circle action is semifree if it is free on the complement to fixed points. We show that a (quasi)toric manifold (in the sense of Davis-Januszkiewicz) over an n-cube with a semifree circle action and isolated fixed points is a Bott tower. Then we show that every Bott tower obtained in this way is topologically trivial, that is, homeomorphic to a product of 2-spheres. This …
Let the circle act in a Hamiltonian fashion on a connected compact symplectic manifold $(M, ω)$ of dimension $2n$. Then the $S^1$-action has at least $n+1$ fixed points. In a previous paper, we study the case when the fixed point set consists of precisely $n+1$ isolated points. In this paper, we study the case when the fixed point set consists of exactly $n+2$ isolated points. We show that in this case $n$ must be even. We find equivalent conditions on the first Chern class of $M$ and a particular weight of the $S^1$-action. We also show that the particular weight can completely determine the …
Consider an effective Hamiltonian circle action on a compact symplectic $2n$-dimensional manifold $(M, ω)$. Assume that the fixed set $M^{S^1}$ is {\em minimal}, in two senses: it has exactly two components, $X$ and $Y$, and $\dim(X) + \dim(Y) = \dim(M) - 2$. We prove that the integral cohomology ring and Chern classes of $M$ are isomorphic to either those of $\CP^n$ or (if $n \neq 1$ is odd) to those of $\Gt_2(\R^{n+2})$, the Grassmannian of oriented two-planes in $\R^{n+2}$. In particular, $H^i(M;\Z) = H^i(\CP^n;\Z)$ for all $i$, and the Chern classes of $M$ are determined by the integral co…
We study the Madsen-Tillman spectrum \CP^\infty_{-1} as a quotient of the Mahowald pro-object \CP^\infty_{-\infty}, which is closely related to the Tate cohomology of circle actions. That theory has an associated symplectic structure, whose symmetries define the Virasoro operations on the cohomology of moduli space constructed by Kontsevich and Witten.
Circle actions and Suspension operations on Smooth manifolds
研究光滑流形上的环动作与悬垂操作，通过环状手术构造并分类具有自由S¹动作的流形。
Given an $S^1$-manifold with isolated fixed points, some recent papers are concerned with the relationship between the least number of fixed points and the characteristic numbers of this manifold, and their proofs have some similar features. The main purpose of this short survey article is, by using the language of equivariant cohomology, to present a unified method to deal with such problems, of which the related known results are direct corollaries.
Circle actions on oriented 4-manifolds
本文研究环作用于定向四维流形的性质，推导Atiyah-Hirzebruch公式，并通过固定点集的数据构建图，证明在孤立固定点情况下，满足该公式的抽象图对应于四维定向S¹-流形。
We specify exterior generators for $π_* THH(MU) = π_*(MU) \otimes E(λ'_n \mid n\ge1)$ and $π_* THH(BP) = π_*(BP) \otimes E(λ_n \mid n\ge1)$, and calculate the action of the $σ$-operator on these graded rings. In particular, $σ(λ'_n) = 0$ and $σ(λ_n) = 0$, while the actions on $π_*(MU)$ and $π_*(BP)$ are expressed in terms of the right units $η_R$ in the Hopf algebroids $(π_*(MU), π_*(MU \wedge MU))$ and $(π_*(BP), π_*(BP \wedge BP))$, respectively.
Hamiltonian circle actions with minimal isolated fixed points
本文研究紧致辛流形上具有最少 $n+1$ 个孤立不动点的哈密顿圆周作用，证明特定权重可完全决定流形的积分上同调环、全陈类及所有不动点权重，并指出这些数据与 $\mathbb{C}P^n$ 或 $\mathbb{G}_2(\mathbb{R}^{n+2})$ 的标准作用同构。
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