アブストラクト事後公開 — 2017年度秋季総合分科会(於:山形大学)
トポロジー分科会
特別講演 写像類群, Goldman–Turaev Lie 双代数, 柏原 Vergne 問題 河澄響矢 (東大数理) Let $\Sigma$ be a compact connected oriented surface with nonempty boundary and a framing $f$. Then a subset of the mapping class group of $\Sigma$, which includes the Torelli group, is naturally embedded into the (completed) Goldman–Turaev Lie bialgebra of $\Sigma$. A framed version of the Turaev cobracket vanishes on the image of the embedding. So we need a formal description of the Goldman–Turaev Lie bialgebra. In the genus $0$ case, the set of expansions inducing a formal description of the bialgebra is naturally bijective to the set of solutions of the Kashiwara–Vergne problem in the formulation of Alekseev–Torossian. In view of this bijection, we can formulate a Kashiwara–Vergne problem associated with $(\Sigma, f)$. The set of its solutions is nonempty except some of the genus $1$ case. This talk is based on a joint work with Anton Alekseev, Yusuke Kuno and Florian Naef. 

2017年度日本数学会幾何学賞受賞特別講演 $3$次元多様体のファイバー曲面とヘガード曲面 作間 誠 (広島大理) Though fiber surfaces and Heegaard surfaces have completely different natures, we can find various analogies between them. We describe the analogies from the view points of (1) the branched fibration theorem, (2) monodromy groups, (3) McShane’s identity and (4) geometric structures. 

特別講演 Sullivan’s coproduct on the reduced loop homology 内藤貴仁 (東大数理) In the theory of string topology initiated by Chas and Sullivan, the homology of free loop spaces of manifolds (called the loop homology) has very rich algebraic structures. The loop product is a multiplication on the loop homology and it is the most basic operation in string topology. Cohen and Godin discovered a 2dimensional TQFT structure on the homology. Moreover, Godin showed that the loop homology is a homological conformal field theory. In this talk, I will discuss a coproduct on the reduced loop homology which is introduced by Sullivan. The coproduct and the loop product give the loop homology an infinitesimal bialgebra structure. I will explain how to construct Sullivan’s coproduct and give some computational examples. 

1. 
Signatures of surface bundles 門田直之 (大阪電通大工) The signature of a surface bundle over a surface has some restrictions, for examples, it is dividable by 4 and vanishes if the base genus is 0 or 1. Bryan and Donagi constructed examples over a genus2 surface with nonzero signatures. However, the signatures and the genera of their examples are sporadic. In this talk, for any positive integer $n$, we give a surface bundle of fiber genus $g$ over a surface of genus 2 with signature $4n$ and a section of selfintersection 0 if $g$ is greater than or equal to $39n$. 

2. 
Stable commutator lengths of Dehn twists 門田直之 (大阪電通大工) In this talk, we give explicit factrizations of certain powers of Dehn twists as products of commutators. As a corollary, we improve upper bounds for stable commutator lengths of Dehn twists. Moreover, we show that the stable commutator length in the mapping class group is different from that in the hyperelliptic mapping class group for a surface of large genus. 

3. 
コルクとそのシャドウ複雑度 直江央寛 (東北大理) For a simply connected closed $4$manifold $M$, any $4$manifold exotic to $M$ is obtained from $X$ by twisting a contractible Stein domain called a cork. We study a cork from a viewpoint of the notion of shadows. A shadow of a $4$manifold is a simple polyhedron collapsed from the manifold. By using a shadow, Costantino defined a complexity of a $4$manifold, which is the minimum number of vertex of its shadow. We show that there are no corks with complexity zero and that there are infinitely many corks with complexity $1$ and $2$. 

4. 
Nonexistence of twists and surgeries generating exotic 4manifolds 安井弘一 (阪大情報) It is well known that for any exotic pair of simply connected closed 4manifolds, one is obtained by twisting the other along a contractible submanifold. In contrast, we show that for each positive integer $n$, there exists an infinite family of pairwise exotic simply connected closed 4manifolds such that, for any 4manifold $X$ and any compact (not necessarily connected) codimension zero submanifold $W$ with $b_1(\partial W)<n$, the family cannot be generated by twisting $X$ along $W$ and varying the gluing map. As a corollary, we show that there exists no ‘universal’ 4manifold with boundary such that any exotic family is generated by twisting along an embedded copy of the 4manifold. Moreover, we give similar results for surgeries. 

5. 
Surfaces in $D^4$ with the same boundary and fundamental group 大場貴裕 (東工大理) This talk is concerned with symplectic surfaces in a symplectic $4$disk $(D^4, \omega)$ bounded by the same transverse link in the standard contact $3$sphere $(S^3, \xi_{st})$. There are some examples of transverse links (or knots) bounding more than two distinct symplectic surfaces. All these surfaces can be distinguished by the fundamental groups of their complements. In this talk, I will present a family of pairs of two distinct symplectic surfaces whose boundaries are the same transverse knot and whose complements have isomorphic fundamental groups. To tell apart the two surfaces of each pair, I take double branched covers branched along them. 

6. 
複素射影構造のノード付き曲面への退化 馬場伸平 (Univ. Heidelberg) A $\mathbb{C}{\rm P}^1$structure on a surface is an atlas modeled on $\mathbb{C}{\rm P}^1$ with transition maps in ${\rm PSL}(2, \mathbb{C})$, and a $\mathbb{C}{\rm P}^1$structure corresponds to a pair of a Riemann surface and a holomorphic quadratic differential on it. In addition, each $\mathbb{C}{\rm P}^1$structure has a holonomy representation from its fundamental group into ${\rm PSL}(2, \mathbb{C})$. In this talk, we consider a path of diverging $\mathbb{C}{\rm P}^1$structures on a closed oriented surface such that, their holonomy representations converge. We discuss about its limit under the assumption that the Riemann surface structures are pinched along some loops. 

7. 
商空間がトーラスとなる対合と可換なリーマン面上の周期的写像の分類 高橋典寿 (立命館大理工)・野沢 啓 (立命館大理工) Ishizaka classified up to conjugation orientation preserving periodic maps of a surface which commute with a hyperelliptic involution. Here, an involution on a surface is hyperelliptic if and only if the quotient space is a sphere. In this talk, we consider maps which commute with involutions whose quotient space is a torus. We will classify up to conjugation orientation preserving irreducible periodic maps which commute with such involutions to give a complete list. It turned out that there are only finite conjugacy classes. We present a representative of each conjugacy class with certain decomposition of surfaces into fundamental domains. 

8. 
Local rigidity of certain actions of nilpotentbycyclic groups on the sphere 岡田真央 (東大数理) Let $G=SU(n,1)$ be the isometry group of complex hyperbolic space $X$ and $G=KAN$ an Iwasawa decomposition. We proved local rigidity of actions of certain finitely generated subgroups $\Gamma$ of $AN$ on the imaginary boundary of $X$. 

9. 
Every lens space contains a genus one homologically fibered knot 野崎雄太 (東大数理) We prove that every lens space contains a genus one homologically fibered knot, which is contrast to the fact that some lens spaces contain no genus one fibered knot. In the proof, the discriminant of a binary quadratic form and the Chebotarev density theorem in number theory play central roles. 

10. 
The spherical growth series for certain Seifert fiber spaces 藤井道彦 (琉球大理) We consider groups presented as $G(p,q)=\langle\ x,\ y \ \ x^p =y^q \ \rangle$, with integers $p$ and $q$ satisfying $2 \leq p \leq q$. The groups are geometrically realized as the fundamental groups of Seifert fiber spaces over 2dimensional disks with two cone points. We present rational function expressions for the spherical growth series of such groups with respect to the generating set $\{x,y,x^{1},y^{1}\}$. 

11. 
結び目のスプライス和で与えられるホモロジー3球面の$\mathit{SL}(2;\mathbb{C})$既約表現のReidemeister torsionの値の有限性について 北野晃朗 (創価大理工) Let $M$ be a homology 3sphere. Reidemeister torsion is a topological invariant of $M$ with a representation $\rho:\pi_1(M)\rightarrow \mathit{SL}(2;\mathbb{C})$. It gives a complex valued function on the space of conjugacy classes of $\mathit{SL}(2;\mathbb{C})$irreducible representations. We show the image is a finite set for some splicing manifolds along torus knots or the figureeight knot. 

12. 
Exceptional Dehn surgeries along the Mazur link 山田裕一 (電通大) A hyperbolic 3manifold that has torus boundaries can change to a nonhyperbolic 3manifold by filling the boundary by a solid torus. Such surgeries are called exceptional surgeries. We study the exceptional Dehn surgeries along the Mazur link and Akbulut–Yasui links. 

13. 
An approach to defining Hempel distance of generalized Heegaard splittings 斎藤敏夫 (上越教育大) It is known that Hempel distance of Heegaard splittings has a good relationship with topology and geometry of 3manifolds. We discuss an approach to defining Hempel distance of generalized Heegaard splittings. 

14. 
Generic閉曲線の一般化された連結和に対するArnold不変量の公式 境 圭一 (信州大理)・杉山龍太郎 We define the generalized connected sum for generic closed plane curves, generalizing the strange sum defined by Arnold, and completely describe how the Arnold invariants $J^{\pm}$ and $\mathit{St}$ behave under the generalized connected sums. 

15. 
Type 1のlensを含む(2,4,2)型のminimal 5chartについて 石上 茜 (東海大理) Let $\Gamma$ be a chart. For each label $k$, we denote by $\Gamma_k$ the union of edges of label $k$ and their vertices. Let $\Gamma$ be a chart. If $\Gamma$ has exactly 8 white vertices and $\Gamma_m \cap \Gamma_{m+1}$ has 2 white vertices, $\Gamma_{m+1} \cap \Gamma_{m+2}$ has 4 white vertices, $\Gamma_{m+2} \cap \Gamma_{m+3}$ has 2 white vertices, then $\Gamma$ is called a chart of type (2,4,2). In this talk we study for a minimal 5chart of type (2,4,2) with a lens of type 1 which has less than or equal to 14 black vertices. 

16. 
1ハンドル付加による被覆曲面結び目の単純化 中村伊南沙 (東大数理) We consider a surfaceknot in the form of a simple branched covering over an oriented surfaceknot $F$, which is called a covering surfaceknot over $F$. Such a surfaceknot is presented by a certain graph called a chart on a surface diagram of $F$. For a covering surfaceknot, an addition of 1handles with chart loops is a simplifying operation which deforms the chart to a union of free edges and 1handles with chart loops. Here, we obtain properties of such simplifications. 

17. 
リボン曲面タングルと曲面絡み目のダブル 佐藤 進 (神戸大理) A ribbon surfacetangle is a compact surface in upper fourspace with no minimal points such that the boundary presents a trivial link. Any surfacelink is the closure of some ribbon surfacetangle. We introduce an equivalence relation among ribbon surfacetangles, called a rootequivalence, and prove that the closures of two ribbon surfacetangles present the same surfacelink if and only if they are rootequivalent. As an application, we see that the double of a surfacelink is welldefined up to stable equivalence. We also study several properties of the double. 

18. 
交差の多重化から得られるウェルデッド絡み目の不変量 宮澤治子 (津田塾大数学・計算機科学研)・和田康載 (早大教育)・安原 晃 (津田塾大学芸) For an ordered $n$component link diagram $D$, we construct a virtual link diagram $D(m_1,m_2,\ldots,m_n)$ which is obtained from $D$ by multiplexing of the crossings of $D$, where $m_i$ is an integer. If two link diagrams $D$ and $D'$ are equivalent, then $D(m_1,m_2,\ldots,m_n)$ and $D'(m_1,m_2,\ldots,m_n)$ are equivalent as welded links. Since an invariant of $D(m_1,m_2,\ldots,m_n)$ is that of $D$, we try to find new invariants of $D$ via $D(m_1,m_2,\ldots,m_n)$. 

19. 
A set of local moves generating the writhe polynomial 中西康剛 (神戸大理)・佐藤 進 (神戸大理) In the talk, we will consider a relationship between an invariant and local moves for virtual knots. We show that two virtual knots have the same writhe polynomial if and only if they are related by a finite sequence of certain local moves. 

20. 
Interior polynomial for signed bipartite graphs and the HOMFLY polynomial 嘉藤桂樹 (東工大理) There are many relations between graph theory and knot theory. In particular, certain knot invariants have been expressed in terms of graph invariants. As an example, the interior polynomial is an invariant of bipartite graphs, and a part of the HOMFLY polynomial of a special alternating link coincides with the interior polynomial of the Seifert graph of the link. We extend the interior polynomial to signed bipartite graphs, and we show that, in the planar case, it is equal to a part of the HOMFLY polynomial of a naturally associated link. We also establish some other, more basic properties of this new notion. This leads to new identities involving the original interior polynomial. 

21. 
仮想結び目のある半順序について 中村拓司 (大阪電通大工)・中西康剛 (神戸大理)・佐藤 進 (神戸大理) For the set of virtual knots $\mathcal{V}$, we define a relation $\leq$ as follows. Let $K,K'$ be virtual knots. We write $K'\leq K$ if for any virtual knot diagram $D$ of $K$, we obtain a virtual knot diagram of $K'$ by replacing several real crossings of $D$ with virtual crossings. In this talk, we show that $(\mathcal{V},\leq)$ is a partially ordered set. We also show that any finite subset of $\mathcal{V}$ has an upper bound with respect to this order. 

22. 
べき単的マグナス展開を用いたMilnor不変量 野坂武史 (東工大)・小谷久寿 We develop a diagrammatic computation of the Milnor invariant of links, in terms of central group extensions and unipotent Magnus embeddings. As a corollary, we compute the invariants of the Milnor link and of some links. We also powerfully extend the higher invariant, by mproving indeterminacy therein. 

23. 
自由群のべき零商の群コサイクル 野坂武史 (東工大) We focus on the cohomology of the $k$th nilpotent quotient of the free group, $F/F_k$. This paper describes all the group 2, 3cocycles in terms of Massey products, and gives expressions for some of the 3cocycles. We also give simple proofs of some of the results on Milnor invariants and the Johnson–Morita homomorphisms. 

24. 
Higherdimensional twisted Alexander invariants for metabelian representations A. T. Tran (Univ. of Texas, Dallas)・山口祥司 (秋田大教育文化) We will discuss the asymptotic behavior of the twisted Alexander invariants for higherdimensional representations of a knot group and the relation to the asymptotic behavior of the Reidemeister torsion. We will focus metabelian representations of a knot group into SL$(2;\mathbb{C})$. It is known that metabelian representations are related to exceptional surgeries along a knot. We will see the relation to our previous result on the asymptotic behavior of the Reidemeister torsion for the resulting manifold obtained by an exceptional surgery along a twist knot. 

25. 
On $n$trivialities of classical and virtual knots for some unknotting operations 伊藤 昇 (東大数理)・櫻井みぎ和 (茨城工高専) In 1990, Vassiliev introduced a filtered space of knot invariants via a standard unknotting operation, called crossing change. In 2000, Goussarov, Polyak, and Viro introduced another degree and filtration via another unknotting operation, called virtualization, for classical and virtual knots. In these theories, a notion of $n$trivialities has played a significant role. However, for an integer $n$ ($> 2$), any example of $n$trivial classical and virtual knot by virtualizations is still missing. In this talk, we obtain an example of $n$trivial knots by virtualizations. We also introduce a new filtration of Vassilievtype invariants by using an unknotting operation, called Forbidden moves. We obtain $n$trivial knots of this new degree. 

26. 
自明な$(2,1)$ケーブル$\Gamma$多項式をもつ結び目の無限族について 滝岡英雄 (阪市大数学研) It is known that there exist many polynomial invariants for knots. For example, Alexander–Conway, Jones, $\Gamma$, $Q$, HOMFLYPT, Kauffman polynomials are well known. These polynomials of the trivial knot are one. The problem is whether there exists a nontrivial knot such that these polynomials are one. It is known that there exists such a knot for the Alexander–Conway, $\Gamma$, $Q$ polynomials. However, it is still an open problem for the other polynomial invariants. Moreover, we consider the $(p,1)$cable versions of these polynomial invariants for an integer $p(\geq 2)$. These $(p,1)$cable versions of the trivial knot are one. The problem is whether there exists a nontrivial knot such that these $(p,1)$cable versions are one. It is known that there exists such a knot for the Alexander–Conway polynomial. However, it is still an open problem for the other polynomial invariants. In this talk, we show that there exist infinitely many knots such that the $(2,1)$cable version of the $\Gamma$polynomial for the knots is one. 

28. 
部分的モノイドにラベルをもつ区間の配置空間 奥山真吾 (香川高専)・島川和久 (岡山大理) A configuration space of intervals in 1dimensional Euclidean space with partially summable labels is constructed. It is a kind of an extension of the configuration space with partially summable labels constructed by the second author and at the same time a generalization of the configuration space of intervals with labels in a based space constructed by the first author. An approximation theorem of the preceding configuration space is generalized to our case. More precisely, we construct a configuration space of intervals in $\mathbb{R}$ with labels in a partial abelian monoid $M$, and show that it is weakly homotopy equivalent to the space of based loops on the classifying space of $M$. 

29. 
Generic linear perturbations 一木俊助 (横浜国大環境情報) In his celebrated paper “Generic projections”, John Mather has shown that almost all linear projections from a submanifold of a vector space into a subspace yield a stable mapping in the nice dimensions. In this talk, an improvement of the Mather result is given. Namely, almost all linear perturbations of a smooth mapping from a submanifold of $\mathbb{R}^m$ into $\mathbb{R}^\ell$ yield a stable mapping in the nice dimensions. 

30. 
Stability of $C^\infty$ convex integrands E. B. Batista (Federal Univ. of Cariri)・韓 呼和 (横浜国大環境情報)・西村尚史 (横浜国大環境情報) In this talk, it is shown that the set consisting of stable convex integrands $S^n\to \mathbb{R}_+$ is open and dense in the set consisting of $C^\infty$ convex integrands with respect to Whitney $C^\infty$ topology. Moreover, it is given examples representing well why stable convex integrands are preferred. 

31. 
写像の特異点集合の自己交差と不足符号数 清水達郎 (京大数理研) We give a geometric proof of that the $k$times selfintersection of singular set of a generic smooth map from $n$dimensional manifold $X$ to $R^p$ coincides with the corank (of Jacobian)$=k$ singular set of any generic map from $X$ to $R^{p+k1}$ as homology classes with $Z/2$ coefficient ($(np+2)k>n+1$). As an application we give a description of the signature defect of framed 3manifold from the point of view of singular sets of maps. 

32. 
Essentially weakly onesided resolving endomorphisms of the shift 那須正和 Characterizations are given for essentially weakly onesided resolving endomorphisms of subshifts. 

33. 
On the limits of onesided resolving directions of endomorphisms of subshifts of finite type 那須正和 We present the results that there exists an automorphism of a full shift having a limit of onesided resolving directions of type II or III and that no automorphism of a transitive subshift of finite type has an irrational unique nonexpansive direction. 

34. 
トポロジカルエントロピーと1次元連続体の幾何学的構造 加藤久男 (筑波大数理物質) In this talk, we define a new notion of “free tracing property by free chains” on $G$like continua and we prove that a positive topological entropy homeomorphism on a $G$like continuum admits a Cantor set $Z$ such that every tuple of finite points in $Z$ is an $IE$tuple of $f$ and $Z$ has the free tracing property by free chains. Also, by use of this notion, we prove the following theorem: If $G$ is any graph and a homeomorphism $f$ on a $G$like continuum $X$ has positive topological entropy, then there is a Cantor set $Z$ which is related to both the chaotic behaviors of Kerr and Li in dynamical systems and composants of indecomposable continua in topology. This theorem implies that chaotic dynamics induce complicated topology. 

35. 
Topological rank does not increase by natural extension of Cantor minimals 下村尚司 (名経大経済) Downarowicz and Maass (2008) defined the topological rank for all homeomorphic Cantor minimal dynamical systems. This definition can be extended to all continuous surjective Cantor minimal systems. We have made it clear that taking natural extension does not increase the topological rank. 

36. 
Proximal Cantor systems with topological rank 2 are residually scrambled 下村尚司 (名経大経済) Downarowicz and Maass (2008) introduced the topological rank on all homeomorphic Cantor minimal dynamical systems. This definition can be easily extended to homeomorphic Cantor proximal dynamical systems. We consider the homeomorphic proximal Cantor dynamical systems with topological rank 2. We show that they are all residually scrambled. Evidently, such systems have at most two ergodic measures. We have obtained a necessary and sufficient condition for the unique ergodicity of these systems. In addition, we show that the number of ergodic measures of systems that are topologically mixing can be 1 and 2. Moreover, there exist examples that are topologically weakly mixing, not topologically mixing, and uniquely ergodic. Finally, we show that the number of ergodic measures of systems that are not weakly mixing can be 1 and 2. 

37. 
Hyperspaces homeomorphic to Hilbert spaces 越野克久 (神奈川大工) Let ${\rm Comp}(X)$ be the hyperspace consisting of nonempty compact subsets of a space $X$ with the Vietoris topology, and ${\rm C}(X)$ be the hyperspace of compact and connected sets in $X$, that is considered as a subspace of ${\rm Comp}(X)$. In this talk, we characterize a metrizable space $X$ whose hyperspaces ${\rm Comp}(X)$ and ${\rm C}(X)$ are homeomorphic to a nonseparable Hilbert space. 

38. 
Local and end deformation theorems for uniform embeddings 矢ヶ崎達彦 (京都工繊大工芸) This talk is concerned with local and end deformation properties of spaces of uniform embeddings in metric manifolds. Using the local deformation theorem by Cernavskii and Edwards–Kirby, we show that any metric manifold with a geometric group action has the local deformation property for uniform embeddings (LD). As an example, the $\kappa$cone end ($\kappa \leq 0$) over any compact Lipschitz metric manifold is shown to have the property (LD). We also introduce a notion of end deformation of uniform embeddings (ED) and show that the 0cone end over any compact Lipschitz metric manifold has the property (ED). A role of uniform isotopies in uniform topology is also clarified. 

39. 
Insertion of posetvalued maps with the waybelow and above relations 山﨑 薫里 (高崎経大経済) We give insertion theorems for maps with values in bibounded complete and bicontinuous posets by using the waybelow relation and the wayabove relation. 