By Fin(X) (resp. $Fi{n}^k\left(X\right)$), we denote the hyperspace of all non-empty finite subsets of X (resp. consisting of at most k points) with the Vietoris topology. Let ℓ₂(τ) be the Hilbert space with weight τ and $\ell {₂}^f\left(\tau \right)$ the linear span of the canonical orthonormal basis of ℓ₂(τ). It is shown that if $E=\ell {₂}^f\left(\tau \right)$ or E is an absorbing set in ℓ₂(τ) for one of the absolute Borel classes ${}_{\alpha }\left(\tau \right)$ and ${}_{\alpha }\left(\tau \right)$ of weight ≤ τ (α > 0) then Fin(E) and each $Fi{n}^k\left(E\right)$ are homeomorphic to E. More generally, if X is a connected E-manifold then Fin(X) is homeomorphic...

If X is a space then L(X) denotes the subspace of C(X) consisting of all Peano (sub)continua. We prove that for n ≥ 3 the space $L\left({ℝ}^n\right)$ is homeomorphic to $B^{\infty }$, where B denotes the pseudo-boundary of the Hilbert cube Q.

Let X be a compact metric space and let C(X) denote the space of subcontinua of X with the Hausdorff metric. It is proved that every two-dimensional continuum X contains, for every n ≥ 1, a one-dimensional subcontinuum $T_n$ with $dimC\left(T_n\right)\ge n$. This implies that X contains a compact one-dimensional subset T with dim C (T) = ∞.

It is shown that the following hyperspaces, endowed with the Hausdorff metric, are true absolute $F_{\sigma \delta }$-sets: (1) ℳ ²₁(X) of Sierpiński universal curves in a locally compact metric space X, provided ℳ ²₁(X) ≠ ∅ ; (2) ℳ ³₁(X) of Menger universal curves in a locally compact metric space X, provided ℳ ³₁(X) ≠ ∅ ; (3) 2-cells in the plane.

Based on some earlier findings on Banach Category Theorem for some “nice” $\sigma$-ideals by J. Kaniewski, D. Rose and myself I introduce the $h$ operator ($h$ stands for “heavy points”) to refine and generalize kernel constructions of A. H. Stone. Having obtained in this way a generalized Kuratowski’s decomposition theorem I prove some characterizations of the domains of functions having “many” points of $h$-continuity. Results of this type lead, in the case of the $\sigma$-ideal of meager sets, to important statements...

For a metric continuum X, let C(X) (resp., $2^X$) be the hyperspace of subcontinua (resp., nonempty closed subsets) of X. Let f: X → Y be an almost continuous function. Let C(f): C(X) → C(Y) and $2^f:2^X\to 2^Y$ be the induced functions given by $C\left(f\right)\left(A\right)=c{l}_Y\left(f\left(A\right)\right)$ and $2^f\left(A\right)=c{l}_Y\left(f\left(A\right)\right)$. In this paper, we prove that: • If $2^f$ is almost continuous, then f is continuous. • If C(f) is almost continuous and X is locally connected, then f is continuous. • If X is not locally connected, then there exists an almost continuous function f: X → [0,1] such that...

We construct examples of mappings $f$ and $g$ between locally connected continua such that $2^f$ and $C\left(f\right)$ are near-homeomorphisms while $f$ is not, and $2^g$ is a near-homeomorphism, while $g$ and $C\left(g\right)$ are not. Similar examples for refinable mappings are constructed.