A locally connected continuum without convergent sequences

Closed locally path-connected subspaces of finite-dimensional groups are locally compact

We prove that each closed locally continuum- connected subspace of a finite dimensional topological group is locally compact. This allows us to construct many 1-dimensional metrizable separable spaces that are not homeomorphic to closed subsets of finite-dimensional topological groups, which answers in negative a question of D.Shakhmatov. Another corollary is a characterization of Lie groups as finite-dimensional locally continuum-connected topological groups. For locally path connected topological groups this characterization was proved by Gleason and Palais in 1957.

Fibers and local connectedness of planar continua

We describe non-locally connected planar continua via the concepts of fiber and numerical scale. Given a continuum $X\subset\mathbb{C}$ and $x\in\partial X$, we show that the set of points $y\in \partial X$ that cannot be separated from $x$ by any finite set $C\subset \partial X$ is a continuum. This continuum is called the {\em modified fiber} $F_x^*$ of $X$ at $x$. If $x\in X^o$, we set $F^*_x=\{x\}$. For $x\in X$, we show that $F_x^*=\{x\}$ implies that $X$ is locally connected at $x$. We also give a concrete planar continuum $X$, which is locally connected at a point $x\in X$ while the fib…

Non-degenerate locally connected models for plane continua and Julia sets

Suppose that a $X$ is an \emph{unshielded} plane continuum (i.e., $X$ coincides with the boundary of the unbounded complementary component of $X$). Then there exists a \emph{finest monotone} map $m:X\to L$, where $L$ is a locally connected continuum (i.e., $m^{-1}(y)$ is connected for each $y\in L$, and any monotone map $φ:X\to L'$ onto a locally connected continuum is a composition $φ=φ'\circ m$ where $φ':L\to L'$ is monotone). Such finest locally connected model $L$ of $X$ is easier to understand because $L$ is locally connected (in particular it can be described by a picture) and represents…

More monotone open homogeneous locally connected plane continua

This paper constructs a continuous decomposition of the Sierpiński curve into acyclic continua one of which is an arc. This decomposition is then used to construct another continuous decomposition of the Sierpiński curve. The resulting decomposition space is homeomorphic to the continuum obtained from taking the Sierpiński curve and identifying two points on the boundary of one of its complementary domains. This outcome is shown to imply that there are continuum many topologically different one dimensional locally connected plane continua that are homogeneous with respect to monotone open maps…

论广义 $V^n$-连续统

On generalized $V^n$-continua

本文研究 $V^n$-连续统的上同调推广，证明强局部齐次且上同调维数为 $n$ 的广义连续统是广义 $V^n$-空间，并得到相应的 Mazurkiewicz 型不可分割定理。

Locally connected models for Julia sets

Let $P$ be a polynomial with a connected Julia set $J$. We use continuum theory to show that it admits a \emph{finest monotone map $\ph$ onto a locally connected continuum $J_{\sim_P}$}, i.e. a monotone map $\ph:J\to J_{\sim_P}$ such that for any other monotone map $ψ:J\to J'$ there exists a monotone map $h$ with $ψ=h\circ \ph$. Then we extend $\ph$ onto the complex plane $\C$ (keeping the same notation) and show that $\ph$ monotonically semiconjugates $P|_{\C}$ to a \emph{topological polynomial $g:\C\to \C$}. If $P$ does not have Siegel or Cremer periodic points this gives an alternative proo…

Approximations by disjoint continua and a positive entropy conjecture

E.D. Tymchatyn constructed a hereditarily locally connected continuum which can be approximated by a sequence of mutually disjoint arcs. We show the example re-opens a conjecture of G.T. Seidler and H. Kato about continua which admit positive entropy homeomorphisms. We prove that every indecomposable semicontinuum can be approximated by a sequence of disjoint subcontinua, and no composant of an indecomposable continuum can be embedded into a Suslinian continuum. We also prove that if $Y$ is a hereditarily unicoherent Suslinian continuum, then there exists $\varepsilon>0$ such that every two $\…

Locally finite trees and the topological minor relation

A well-known theorem of Nash-Williams shows that the collection of locally finite trees under the topological minor relation results in a BQO. Set theoretically, two very natural questions arise: (1) What is the number $λ$ of topological types of locally finite trees? (2) What are the possible sizes of an equivalence class of locally finite trees? For (1), clearly, $ω\leq λ\leq \mathfrak{c}$ and Matthiesen refined it to $ω_1 \leq λ\leq \mathfrak{c}$. Thus, this question becomes non-trivial when the Continuum Hypothesis is not assumed. In this paper we address both questions by showing that - e…

关于带附加零元的半群 $\mathscr{C}_{+}(a,b)$ 和 $\mathscr{C}_{-}(a,b)$ 上的局部紧移位连续拓扑

On locally compact shift-continuous topologies on semigroups $\mathscr{C}_{+}(a,b)$ and $\mathscr{C}_{-}(a,b)$ with adjoined zero

本文研究了带附加零元的半群 $\mathscr{C}_{+}(a,b)$ 和 $\mathscr{C}_{-}(a,b)$，证明其在拓扑同构意义下存在连续统许多不同的 Hausdorff 局部紧移位连续拓扑。