No Arabic abstract
In our earlier papers we constructed examples of 2-dimensional nonaspherical simply-connected cell-like Peano continua, called {sl Snake space}. In the sequel we introduced the functor $SC(-,-)$ defined on the category of all spaces with base points and continuous mappings. For the circle $S^1$, the space $SC(S^1, ast)$ is a Snake space. In the present paper we study the higher-dimensional homology and homotopy properties of the spaces $SC(Z, ast)$ for any path-connected compact spaces $Z$.
We prove the existence of a 2-dimensional nonaspherical simply connected cell-like Peano continuum (the space itself was constructed in one of our earlier papers). We also indicate some relations between this space and the well-known Griffiths space from the 1950s.
We attach copies of the circle to points of a countable dense subset $D$ of a separable metric space $X$ and construct an earring space $E(X,D)$. We show that the fundamental group of $E(X,D)$ is isomorphic to a subgroup of the Hawaiian earring group, if the space $X$ is simply-connected and locally simply-connected. In addition if the space $X$ is locally path-connected, the space $X$ can be recovered from the fundamental group of $E(X,D)$.
Using the topologist sine curve we present a new functorial construction of cone-like spaces, starting in the category of all path-connected topological spaces with a base point and continuous maps, and ending in the subcategory of all simply connected spaces. If one starts by a noncontractible n-dimensional Peano continuum for any n>0, then our construction yields a simply connected noncontractible (n + 1)-dimensional cell-like Peano continuum. In particular, starting with the circle $mathbb{S}^1$, one gets a noncontractible simply connected cell-like 2-dimensional Peano continuum.
Given a collection of pairwise co-prime integers $% m_{1},ldots ,m_{r}$, greater than $1$, we consider the product $Sigma =Sigma _{m_{1}}times cdots times Sigma _{m_{r}}$, where each $Sigma _{m_{i}}$ is the $m_{i}$-adic solenoid. Answering a question of D. P. Bellamy and J. M. L ysko, in this paper we prove that if $M$ is a subcontinuum of $Sigma $ such that the projections of $M$ on each $Sigma _{m_{i}}$ are onto, then for each open subset $U$ in $Sigma $ with $Msubset U$, there exists an open connected subset $V$ of $Sigma $ such that $Msubset Vsubset U$; i.e. any such $M$ is ample in the sense of Prajs and Whittington [10]. This contrasts with the property of Cartesian squares of fixed solenoids $Sigma _{m_{i}}times Sigma _{m_{i}}$, whose diagonals are never ample [1].
Given a Lie group $G$ we study the class $M$ of proper metrizable $G$-spaces with metrizable orbit spaces, and show that any $G$-space $X in M$ admits a closed $G$-embedding into a convex $G$-subset $C$ of some locally convex linear $G$-space, such that $X$ has some $G$-neighborhood in $C$ which belongs to the class $M$. As corollaries we see that any $G$-ANE for $M$ has the $G$-homotopy type of some $G$-CW complex and that any $G$-ANR for $M$ is a $G$-ANE for $M$.