Spin^c structures and homotopy equivalences

Factorization of homotopies of nanophrases

Homotopy on nanophrases is an equivalence relation defined using some data called a homotopy data triple. We define a product on homotopy data triples. We show that any homotopy data triple can be factorized into a product of prime homotopy data triples and this factorization is unique up to isomorphism and order. If a homotopy data triple is composite, we show that equivalence of nanophrases under the corresponding homotopy can be calculated just by using the homotopies given by its prime factors.

Homotopy self-equivalences of 4-manifolds

We establish a braid of interlocking exact sequences containing the group of homotopy self-equivalences of a smooth or topological 4-manifold. The braid is computed for manifolds whose fundamental group is finite of odd order.

s-Cobordism classification of $4$-manifolds through the group of homotopy self-equivalences

The aim of this paper is to give an $s$-cobordism classification of topological $4$-manifolds in terms of the standard invariants using the group of homotopy self-equivalences. Hambleton and Kreck constructed a braid to study the group of homotopy self-equivalences of $4$-manifolds. Using this braid together with the modified surgery theory of Kreck, we give an $s$-cobordism classification for certain $4$-manifolds with fundamental group $π$, such that cd $π\leq 2$.

An equivalence between the set of graph-knots and the set of homotopy classes of looped graphs

In the present paper we construct a one-to-one correspondence between the set of graph-knots and the set of homotopy classes of looped graphs. Moreover, the graph-knot and the homotopy class constructed from a given knot are related with this correspondence. This correspondence is given by a simple formula.

图的真同伦等价的复杂性

The Complexity of Proper Homotopy Equivalence of Graphs

该研究证明局部有限图的真同伦等价关系是博雷尔完全的，发现无限图中存在comeager等价类，并由此推出带裤子分解的非紧曲面同胚关系的类似结论。

A remark on the homotopy equivalence of SU_n and SL_nC

Being a maximal compact subgroup of SL_nC, SU_n is a deformation retract of the former group. In this note we prove that, for sufficiently large n, there is no retraction of SL_nC to SU_n which preserves commutativity.

Isotopy and Homotopy Invariants of Classical and Virtual Pseudoknots

Pseudodiagrams are knot or link diagrams where some of the crossing information is missing. Pseudoknots are equivalence classes of pseudodiagrams, where equivalence is generated by a natural set of Reidemeister moves. In this paper, we introduce a Gauss-diagrammatic theory for pseudoknots which gives rise to the notion of a virtual pseudoknot. We provide new, easily computable isotopy and homotopy invariants for classical and virtual pseudodiagrams. We also give tables of unknotting numbers for homotopically trivial pseudoknots and homotopy classes of homotopically nontrivial pseudoknots. Sinc…

Homotopy invariants of Gauss phrases

Equivalence relations can be defined on Gauss phrases using combinatorial moves. In this paper we consider two closely related equivalence relations on Gauss phrases, homotopy and open homotopy. In particular, in each case, we define a new invariant and determine the values that it can attain.

Counting open negatively curved manifolds up to tangential homotopy equivalence

Under mild assumptions on a group G, we prove that the class of complete Riemannian n-manifolds of uniformly bounded negative sectional curvatures and with the fundamental groups isomorphic to G breaks into finitely many tangential homotopy types. It follows that many aspherical manifolds do not admit complete negatively curved metrics with prescribed curvature bounds.

On a notion of maps between orbifolds, II. homotopy and CW-complex

This is the second of a series of papers which are devoted to a comprehensive theory of maps between orbifolds. In this paper, we develop a basic machinery for studying homotopy classes of such maps. It contains two parts: (1) the construction of a set of algebraic invariants -- the homotopy groups, and (2) an analog of CW-complex theory. As a corollary of this machinery, the classical Whitehead theorem which asserts that a weak homotopy equivalence is a homotopy equivalence is extended to the orbifold category.

The Uniform Homotopy Category

This paper gives a uniform-theoretic refinement of classical homotopy theory. Both cubical sets (with connections) and uniform spaces admit classes of weak equivalences, special cases of classical weak equivalences, appropriate for the respective Lipschitz and uniform settings. Cubical sets and uniform spaces admit the additional compatible structures of categories of (co)fibrant objects. A categorical equivalence between classical homotopy categories of cubical sets and spaces lifts to a full and faithful embedding from an associated Lipschitz homotopy category of cubical sets into an associa…

RP²×S²的同伦自等价与非定向4维流形的辫子

Homotopy Self-Equivalences of $\mathbb{R}P^2\times S^2$ and a Braid for non-orientable $4$-Manifolds

该研究计算了RP²×S²的基于自同伦等价类群，构造了非定向4维流形的辫子正合序列，确定了Hambleton–Hillman流形的正规1型，还分析了RP²×S²的捏折映射性质。

环路余积的同伦同调不变性

Simple homotopy invariance of the loop coproduct

本文证明了弦拓扑中 Goresky-Hingston 环路余积在流形同伦等价下的变换公式，指出其涉及 Whitehead 挠率的迹，并揭示了该余积在简单同伦等价下的不变性及其在 2 维 TQFT 中的拓扑起源。

4-流形上的稳定等价关系

Stable equivalence relations on 4-manifolds

该研究结合改进式与经典手术理论，研究4-流形的多种稳定等价关系，证明阿贝尔基本群的闭可定向同伦等价4-流形稳定微分同胚，给出稳定同胚消去定理对应版本及相关代数障碍。

Simple Homotopy Types and Finite Spaces

We present a new approach to simple homotopy theory of polyhedra using finite topological spaces. We define the concept of collapse of a finite space and prove that this new notion corresponds exactly to the concept of a simplicial collapse. More precisely, we show that a collapse of finite spaces induces a simplicial collapse of their associated simplicial complexes. Moreover, a simplicial collapse induces a collapse of the associated finite spaces. This establishes a one-to-one correspondence between simple homotopy types of finite simplicial complexes and simple equivalence classes of finit…

端周期图映射的映射环面嵌入

Embeddings of mapping tori for end-periodic graph maps

该研究探讨无限局部有限图的端周期同伦等价，证明其映射环面可与有限2-复形保流线同伦等价，附加假设下可π₁-单射保流嵌入有限秩图映射环面，且每个此类映射类含实现该嵌入的代表。

自等价与配边的编织

Braidings of Self-Equivalences and Bordism

针对n≥4的闭光滑或拓扑流形，通过构造同伦高度笛卡尔正方形建立自等价空间与法配边理论环空间的关联，推广了Hambleton–Kreck的相关工作。

An infinite-dimensional phenomenon in finite-dimensional metric topology

We show that there are homotopy equivalences $h:N\to M$ between closed manifolds which are induced by cell-like maps $p:N\to X$ and $q:M\to X$ but which are not homotopic to homeomorphisms. The phenomenon is based on construction of cell-like maps that kill certain $\mathbb L$-classes. The image space in these constructions is necessarily infinite-dimensional. In dimension $>6$ we classify all such homotopy equivalences. As an application, we show that such homotopy equivalences are realized by deformations of Riemannian manifolds in Gromov-Hausdorff space preserving a contractibility function…

论弦拓扑余积的不变性

On the invariance of the string topology coproduct

研究弦拓扑余积在同伦等价下不变性失效问题，给出基于同伦数据及“伪对角线”构建阻碍类的奈夫公式变体，此阻碍类可衡量同伦等价有界性，且决定余积到高维环路推广的不变性失效。

从分层同伦视角看稳定曲线的模栈

Moduli stack of stable curves from a stratified homotopy viewpoint

本文加强了Charney和Lee的结果，证明了稳定曲线范畴能捕获模栈的分层同伦类型，并通过外行进等价对可构造层进行分类。

通过参数化不动点理论探讨同伦不变性的障碍

Obstructions to homotopy invariance of loop coproduct via parametrised fixed-point theory

本文通过参数化不动点理论探讨同伦不变性的障碍，定义Reidemeister迹并表征谱余乘积的失败，揭示简单同伦等价下谱余乘积的一致性。