On the topological full group containing the Grigorchuk group

Thue-Morse序列与中间增长群

Thue-Morse sequence and groups of intermediate growth

本文通过嵌入Grigorchuk群到Thue-Morse替换生成的子移位的拓扑全群中，证明了该群包含一个中间增长子群。

关于拓扑全群的顺从性与LEF性质

On Amenability and LEF-ness for topological full groups

本文证明了拓扑自由远端作用的拓扑全群顺从性等价于底群顺从，并推广了LEF性质到剩余有限作用，进而证明自由群上某些Toeplitz子位移的拓扑全群是LEF且sofic。

On the spread of topological groups containing subsets of the Sorgenfrey line

We prove that any topological group $G$ containing a subspace $X$ of the Sorgenfrey line has spread $s(G)\ge s(X\times X)$. Under OCA, each topological group containing an uncountable subspace of the Sorgenfrey line has uncountable spread. This implies that under OCA a cometrizable topological group $G$ is cosmic if and only if it has countable spread. On the other hand, under CH there exists a cometrizable Abelian topological group that has hereditarily Lindelöf countable power and contains an uncountable subspace of the Sorgenfrey line. This cometrizable topological group has countable sprea…

On topological groups containing a Fréchet-Urysohn fan

Suppose G is a topological group containing a (closed) topological copy of the Frechet-Urysohn fan. If G is a perfectly normal sequential space (a normal k-space) then every closed metrizable subset in $G$ is locally compact. Applying this result to topological groups whose underlying topological space can be written as a direct limit of a sequence of closed metrizable subsets, we get that every such a group either is metrizable or is homeomorphic to the product of a $k_ω$-space and a discrete space.

由因子映射和子群胚产生的拓扑全群的最大子群

Maximal subgroups of topological full groups arising from factor maps and subgroupoids

本文通过因子映射和宽开子群胚构造拓扑全群及其换位子群的最大子群，给出最大性判据，并应用于康托尔极小系统，产生 Grigorchuk-Vorobets 猜想中的划分稳定化子及顺从群中的最大子群例子。

拓扑全群的稳定子与极大子群

Stabilizers and maximal subgroups of topological full groups

该研究将Grigorchuk等人的极大稳定子定理推广到含换位子群的子群，证明了极小作用稳定子的空间刚性，实现了AF群胚的限制，得到连续多个不同构极大稳定子及C*-代数的AF子商。

Embedding the bicyclic semigroup into countably compact topological semigroups

We study algebraic and topological properties of topological semigroups containing a copy of the bicyclic semigroup C(p,q). We prove that each topological semigroup S with pseudocompact square contains no dense copy of C(p,q). On the other hand, we construct a (consistent) example of a pseudocompact (countably compact) Tychonov semigroup containing a copy of C(p,q).

Each topological group embeds into a duoseparable topological group

A topological group $X$ is called $duoseparable$ if there exists a countable set $S\subseteq X$ such that $SUS=X$ for any neighborhood $U\subseteq X$ of the unit. We construct a functor $F$ assigning to each (abelian) topological group $X$ a duoseparable (abelain-by-cyclic) topological group $FX$, containing an isomorphic copy of $X$. In fact, the functor $F$ is defined on the category of unital topologized magmas. Also we prove that each $σ$-compact locally compact abelian topological group embeds into a duoseparable locally compact abelian-by-countable topological group.

Graph 4-braid groups and Massey products

We first show that the braid group over a graph topologically containing no $Θ$-shape subgraph has a presentation related only by commutators. Then using discrete Morse theory and triple Massey products, we prove that a graph topologically contains none of four prescribed graphs if and only if its 4-braid groups is a right-angled Artin group.

Completing Artin's braid group on infinitely many strands

A generalization of the topological fundamental group is developed in order to exhibit a topologically complete braid group containing Artin's braid group on infinitely many strands with respect to the following notion of convergence: A sequence of braids b(n) converges to the trivial braid iff for each M>0 eventually the first M strands of b(n) are trivial.

A quantitative generalization of Prodanov-Stoyanov Theorem on minimal Abelian topological groups

A topological group $X$ is defined to have $compact$ $exponent$ if for some number $n\in\mathbb N$ the set $\{x^n:x\in X\}$ has compact closure in $X$. Any such number $n$ will be called a compact exponent of $X$. Our principal result states that a complete Abelian topological group $X$ has compact exponent (equal to $n\in\mathbb N$) if and only if for any injective continuous homomorphism $f:X\to Y$ to a topological group $Y$ and every $y\in \bar{f(X)}$ there exists a positive number $k$ (equal to $n$) such that $y^k\in f(X)$. This result has many interesting implications: (1) an Abelian topo…

有限型移位的拓扑全群的极大子群

Maximal subgroups of topological full groups of shifts of finite type

该研究探讨有限型移位拓扑全群的极大子群，证明素子群胚的三分性，给出其拓扑全群正规化子为极大的判据，扩展Thompson群V相关结果并得到含交换子群的子群的极大子群数量结论。