Searcharxiv⌕ Search

arXiv subjects

Shicheng Wang

Publications and source records attributed to Shicheng Wang.

At least 37 records · Page 2Linked to original sources
arXiv2017

Graphs in the 3--sphere with maximum symmetry

We consider the orientation-preserving actions of finite groups $G$ on pairs $(S^3, Γ)$, where $Γ$ is a connected graph of genus $g>1$, embedded in $S^3$. For each $g$ we give the maximum order $m_g$ of such $G$ acting on $(S^3, Γ)$ for all such $Γ\subset S^3$. Indeed we will classify all graphs $Γ\subset S^3$ which realize these $m_g$ in different levels: as abstract graphs and as spatial graphs, as well as their group actions. Such maximum orders without the condition "orientation-preserving" are also addressed.

math.GT↗
arXiv2017

Bordered surfaces in the 3-sphere with maximum symmetry

We consider orientation-preserving actions of finite groups $G$ on pairs $(S^3, Σ)$, where $Σ$ denotes a compact connected surface embedded in $S^3$. In a previous paper, we considered the case of closed, necessarily orientable surfaces, determined for each genus $g>1$ the maximum order of such a $G$ for all embeddings of a surface of genus $g$, and classified the corresponding embeddings. In the present paper we obtain analogous results for the case of bordered surfaces $Σ$ (i.e. with non-empty boundary, orientable or not). Now the genus $g$ gets replaced by the algebraic genus $α$ of $Σ$ (the rank of its free fundamental group); for each $α> 1$ we determine the maximum order $m_α$ of an action of $G$, classify the topological types of the corresponding surfaces (topological genus, number of boundary components, orientability) and their embeddings into $S^3$. For example, the maximal possibility $12(α- 1)$ is obtained for the finitely many values $α= 2, 3, 4, 5, 9, 11, 25, 97, 121$ and $241$.

math.GT↗
arXiv2017

Embedding compact surfaces into the 3-dimensional Euclidean space with maximum symmetry

The symmetries of surfaces which can be embedded into the symmetries of the 3-dimensional Euclidean space $\mathbb{R}^3$ are easier to feel by human's intuition. We give the maximum order of finite group actions on $(\mathbb{R}^3, Σ)$ among all possible embedded closed/bordered surfaces with given geometric/algebraic genus $>1$ in $\mathbb{R}^3$. We also identify the topological types of the bordered surfaces realizing the maximum order, and find simple representative embeddings for such surfaces.

math.GT↗
arXiv2017

Volume of representations and mapping degree

Given a connected real Lie group and a contractible homogeneous proper $G$--space $X$ furnished with a $G$--invariant volume form, a real valued volume can be assigned to any representation $ρ\colon π_1(M)\to G$ for any oriented closed smooth manifold $M$ of the same dimension as $X$. Suppose that $G$ contains a closed and cocompact semisimple subgroup, it is shown in this paper that the set of volumes is finite for any given $M$. From a perspective of model geometries, examples are investigated and applications with mapping degrees are discussed.

math.GT↗
arXiv2017

Invariant incompressible surfaces in reducible 3-manifolds

We study the effect of the mapping class group of a reducible 3-manifold $M$ on each incompressible surface that is invariant under a self-homeomorphism of $M$. As an application of this study we answer a question of F. Rodriguez Hertz, M. Rodriguez Hertz and R. Ures: A reducible 3-manifold admits an Anosov torus if and only if one of its prime summands is either the 3-torus, the mapping torus of $-id$, or the mapping torus of a hyperbolic automorphism.

math.GT↗
arXiv2016

Positive simplicial volume implies virtually positive Seifert volume for $3$-manifolds

In this paper, it is shown that for any closed orientable $3$-manifold with positive simplicial volume, the growth of the Seifert volume of its finite covers is faster than the linear rate. In particular, each closed orientable $3$-manifold with positive simplicial volume has virtually positive Seifert volume. The result reveals certain fundamental difference between the representation volume of the hyperbolic type and the Seifert type. The proof is based on developments and reactions of recent results on virtual domination and on virtual representation volumes of $3$-manifolds.

math.GT↗
arXiv2016

Embedding surfaces into $S^3$ with maximum symmetry

We restrict our discussion to the orientable category. For $g > 1$, let $OE_g$ be the maximum order of a finite group $G$ acting on the closed surface $Σ_g$ of genus $g$ which extends over $(S^3, Σ_g)$, where the maximum is taken over all possible embeddings $Σ_g\hookrightarrow S^3$. We will determine $OE_g$ for each $g$, indeed the action realizing $OE_g$. In particular, with 23 exceptions, $OE_g$ is $4(g+1)$ if $g\ne k^2$ or $4(\sqrt{g}+1)^2$ if $g=k^2$, and moreover $OE_g$ can be realized by unknotted embeddings for all $g$ except for $g=21$ and $481$.

math.GT↗
arXiv2016

The most symmetric surfaces in the 3-torus

Suppose an orientation preserving action of a finite group $G$ on the closed surface $Σ_g$ of genus $g>1$ extends over the 3-torus $T^3$ for some embedding $Σ_g\subset T^3$. Then $|G|\le 12(g-1)$, and this upper bound $12(g-1)$ can be achieved for $g=n^2+1, 3n^2+1, 2n^3+1, 4n^3+1, 8n^3+1, n\in \mathbb{Z}_+$. Those surfaces in $T^3$ realizing the maximum symmetries can be either unknotted or knotted. Similar problems in non-orientable category is also discussed. Connection with minimal surfaces in $T^3$ is addressed and when the maximum symmetric surfaces above can be realized by minimal surfaces is identified.

math.GT↗
arXiv2015

1-domination of knots

We say that a knot $k_1$ in the $3$-sphere {\it $1$-dominates} another $k_2$ if there is a proper degree 1 map $E(k_1) \to E(k_2)$ between their exteriors, and write $k_1 \ge k_2$. When $k_1 \ge k_2$ but $k_1 \ne k_2$ we write $k_1 > k_2$. One expects in the latter eventuality that $k_1$ is more {\it complicated}. In this paper we produce various sorts of evidence to support this philosophy.

math.AT↗
arXiv2013

Chern--Simons theory, surface separability, and volumes of 3-manifolds

We study the set ${\rm vol}\left(M,G\right)$ of volumes of all representations $ρ\coπ_1M\to G$, where $M$ is a closed oriented $3$-manifold and $G$ is either ${\rm Iso}_+{\Hi}^3$ or ${\rm Iso}_e\t{\rm SL_2(\R)}$. By various methods, including relations between the volume of representations and the Chern--Simons invariants of flat connections, and recent results of surfaces in 3-manifolds, we prove that any 3-manifold $M$ with positive Gromov simplicial volume has a finite cover $\t M$ with ${\rm vol}(\t M,{\rm Iso}_+{\Hi}^3)\ne \{0\}$, and that any non-geometric 3-manifold $M$ containing at least one Seifert piece has a finite cover $\t M$ with ${\rm vol}(\t M,{\rm Iso}_e\t{\rm SL_2(\R)}) \ne \{0\}$. We also find 3-manifolds $M$ with positive simplicial volume but ${\rm vol}(M,{\rm Iso}_+{\Hi}^3)=\{0\}$, and non-trivial graph manifolds $M$ with ${\rm vol}(M,{\rm Iso}_e\t{\rm SL_2(\R)})=\{0\}$, proving that it is in general necessary to pass to some finite covering to guarantee that ${\rm vol}(M,G)\not=\{0\}$. Besides we determine ${\rm vol}\left(M, G \right)$ when $M$ supports the Seifert geometry.

math.GT↗
arXiv2013

On slope genera of knotted tori in 4-space

In this note, we investigate genera for the slopes of a knotted torus in the 4-sphere analogous to the genus of a classical knot. We compare various formulations of this notion, and use this notion to study the extendable subgroup of the mapping class group of the knotted torus.

math.GT↗
arXiv2013

Embedding periodic maps on surfaces into those on $S^3$

Call a periodic map $h$ on the closed orientable surface $Σ_g$ extendable if $h$ extends to a periodic map over the pair $(S^3, Σ_g)$ for possible embeddings $e: Σ_g\to S^3$. We determine the extendabilities for all periodical maps on $Σ_2$. The results involve various orientation preserving/reversing behalves of the periodical maps on the pair $(S^3, Σ_g)$. To do this we first list all periodic maps on $Σ_2$, and indeed we exhibit each of them as a composition of primary and explicit symmetries, like rotations, reflections and antipodal maps, which itself should be an interesting piece. A by-product is that for each even $g$, the maximum order periodic map on $Σ_g$ is extendable, which contrasts sharply to the situation in orientation preserving category.

math.GT↗
arXiv2012

Extending finite group actions on surfaces over $S^3$

Let $OE_g$ (resp. $CE_g$ and $AE_g$) and resp. $OE^o_g$ be the maximum order of finite (resp. cyclic and abelian) groups $G$ acting on the closed orientable surfaces $Σ_g$ which extend over $(S^3, Σ_g)$ among all embeddings $Σ_g\to S^3$ and resp. unknotted embeddings $Σ_g\to S^3$. It is known that $OE^o_g\le 12(g-1)$, and we show that $12(g-1)$ is reached for an unknotted embedding $Σ_g \to S^3$ if and only if $g = 2$, 3, 4, 5, 6, 9, 11, 17, 25, 97, 121, 241, 601. Moreover $AE_g$ is $2g+2$; and $CE_g$ is $2g+2$ for even $g$, and $2g-2$ for odd $g$. Efforts are made to see intuitively how these maximal symmetries are embedded into the symmetries of the 3-sphere.

math.GT↗
arXiv2011

Chern Simons Theory and the volume of 3-manifolds

We give some applications of the Chern Simons gauge theory to the study of the set ${\rm vol}(N,G)$ of volumes of all representations $ρ\coπ_1N\to G$, where $N$ is a closed oriented three-manifold and $G$ is either ${\rm Iso}_e\t{\rm SL_2(\R)}$, the isometry group of the Seifert geometry, or ${\rm Iso}_+{\Hi}^3$, the orientation preserving isometry group of the hyperbolic 3-space. We focus on three natural questions: (1) How to find non-zero values in ${\rm vol}(N, G)$? or weakly how to find non-zero elements in ${\rm vol}(\t N, G)$ for some finite cover $\t N$ of $N$? (2) Do these volumes satisfy the covering property in the sense of Thurston? (3) What kind of topological information is enclosed in the elements of ${\rm vol}(N, G)$? We determine ${\rm vol}(N, G)$ when $N$ supports the Seifert geometry, and we find some non-zero values in ${\rm vol}(N,G)$ for certain 3-manifolds with non-trivial geometric decomposition for either $G={\rm Iso}_+{\Hi}^3$ or ${\rm Iso}_e\t{\rm SL_2(\R)}$. Moreover we will show that unlike the Gromov simplicial volume, these non-zero elements carry the gluing information between the geometric pieces of $N$. For a large class 3-manifolds $N$, including all rational homology 3-spheres, we prove that $N$ has a positive Gromov simplicial volume iff it admits a finite covering $\t N$ with ${\rm vol}(\t N,{\rm Iso}_+{\Hi}^3)\ne \{0\}$. On the other hand, among such class, there are some $N$ with positive simplicial volume but ${\rm vol}(N,{\rm Iso}_+{\Hi}^3)=\{0\}$, yielding a negative answer to question (2) for hyperbolic volume.

math.GT↗
arXiv2011

Finiteness of 3-manifolds associated with non-zero degree mappings

We prove a finiteness result for the $\partial$-patterned guts decomposition of all 3-manifolds obtained by splitting a given orientable, irreducible and $\partial$-irreducible 3-manifold along a closed incompressible surface. Then using the Thurston norm, we deduce that the JSJ-pieces of all 3-manifolds dominated by a given compact 3-manifold belong, up to homeomorphism, to a finite collection of compact 3-manifolds. We show also that any closed orientable 3-manifold dominates only finitely many integral homology spheres and any compact 3-manifolds orientable 3-manifold dominates only finitely many exterior of knots in $S^3$.

math.GT↗
arXiv2010

Extending $T^p$ automorphisms over $\RR^{p+2}$ and realizing DE attractors

In this paper we consider the realization of DE attractors by self-diffeomorphisms of manifolds. For any expanding self-map $ϕ:M\to M$ of a connected, closed $p$-dimensional manifold $M$, one can always realize a $(p,q)$-type attractor derived from $ϕ$ by a compactly-supported self-diffeomorphsm of $\RR^{p+q}$, as long as $q\geq p+1$. Thus lower codimensional realizations are more interesting, related to the knotting problem below the stable range. We show that for any expanding self-map $ϕ$ of a standard smooth $p$-dimensional torus $T^p$, there is compactly-supported self-diffeomorphism of $\RR^{p+2}$ realizing an attractor derived from $ϕ$. A key ingredient of the construction is to understand automorphisms of $T^p$ which extend over $\RR^{p+2}$ as a self-diffeomorphism via the standard unknotted embedding $\imath_p:T^p\hookrightarrow\RR^{p+2}$. We show that these automorphisms form a subgroup $E_{\imath_p}$ of $\Aut(T^p)$ of index at most $2^p-1$.

math.GT↗
arXiv2010

Finiteness of mapping degree sets for 3-manifolds

By constructing certain maps, this note completes the answer of the Question: For which closed orientable 3-manifold $N$, the set of mapping degrees $cD(M,N)$ is finite for any closed orientable 3-manifold $M$?

math.GT↗