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Rodrigo Hernández-Gutiérrez

Publications and source records attributed to Rodrigo Hernández-Gutiérrez.

27 records · Page 2Linked to original sources
arXiv2016

Homogeneity degree of some symmetric products

For a metric continuum $X$, we consider the $n^{\tiny\textrm{th}}$-symmetric product $F_{n}(X)$ defined as the hyperspace of all nonempty subsets of $X$ with at most $n$ points. The homogeneity degree $hd(X)$ of a continuum $X$ is the number of orbits for the action of the group of homeomorphisms of $X$ onto itself. In this paper we determine $hd(F_{n}(X))$ for every manifold without boundary and $n\in \mathbb{N}$. We also compute $hd(F_{n}[0,1])$ for all $n\in \mathbb{N}$.

math.GN↗
arXiv2016

A fixed-point-free map of a tree-like continuum induced by bounded valence maps on trees

Towards attaining a better working understanding of fixed points of maps of tree-like continua, Oversteegen and Rogers constructed a tree-like continuum with a fixed-point-free self-map, described explicitly in terms of inverse limits. Specifically, they developed a sequence of trees $T_n$, $n \in \mathbb{N}$ and maps $f_n$ and $g_n$ from $T_{n+1}$ to $T_n$ for each $n$, such that the $g_n$ maps induce a fixed-point-free self-map of the inverse limit space $\varprojlim (T_n,f_n)$. The complexity of the trees and the valences of the maps in their example all grow exponentially with $n$, making it difficult to visualize and compute with their space and map. We construct another such example, in which the maps $f_n$ and $g_n$ have uniformly bounded valence, and the trees $T_n$ have a simpler structure.

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arXiv2016

Uniform Powers of Compacta and the Proximal Game

The countable uniform power (or uniform box product) of a uniform space $X$ is a special topology on ${}^ωX$ that lies between the Tychonoff topology and the box topology. We solve an open problem posed by P. Nyikos showing that if $X$ is a compact proximal space then the countable uniform power of $X$ is also proximal (although it is not compact). By recent results of J. R. Bell and G. Gruenhage this implies that the countable uniform power of a Corson compactum is collectionwise normal, countably paracompact and Fréchet-Urysohn. We also give some results about first countability, realcompactness in countable uniform powers of compact spaces and explore questions by P. Nyikos about semi-proximal spaces.

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arXiv2016

Reversible filters

A space is reversible if every continuous bijection of the space onto itself is a homeomorphism. In this paper we study the question of which countable spaces with a unique non-isolated point are reversible. By Stone duality, these spaces correspond to closed subsets in the Čech-Stone compactification of the natural numbers $βω$. From this, the following natural problem arises: given a space $X$ that is embeddable in $βω$, is it possible to embed $X$ in such a way that the associated filter of neighborhoods defines a reversible (or non-reversible) space? We give the solution to this problem in some cases. It is specially interesting whether the image of the required embedding is a weak $P$-set.

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arXiv2015

Remote Filters and Discretely Generated Spaces

Alas, Junqueira and Wilson asked whether there is a discretely generated locally compact space whose one point compactification is not discretely generated and gave a consistent example using CH. Their construction uses a remote filter in $ω\times{}^ω2$ with a base of order type $ω_1$ when ordered modulo compact subsets. In this paper we study the existence and preservation (under forcing extension) of similar types of filters, mainly using small uncountable cardinals. With these results we show that the CH example can be constructed in more general situations.

math.GN↗
arXiv2014

A Whitney map onto the Long Arc

In a recent paper, Garc\'ıa-Velazquez has extended the notion of Whitney map to include maps with non-metrizable codomain and left open the question of whether there is a continuum that admits such a Whitney map. In this paper, we consider two examples of hereditarily indecomposable, chainable continua of weight $ω_1$ constructed by Michel Smith; we show that one of them admits a Whitney function onto the long arc and the other admits no Whitney maps at all.

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arXiv2013

Periodic points and transitivity on dendrites

We study relations between transitivity, mixing and periodic points on dendrites. We prove that when there is a point with dense orbit which is not an endpoint, then periodic points are dense and there is a terminal periodic decomposition (we provide an example of a dynamical system on a dendrite with dense endpoints satisfying this assumption). We also show that it may happen that all periodic points except one (and points with dense orbit) are contained in the (dense) set of endpoints. It may also happen that dynamical system is transitive but there is a unique periodic point, which in fact is the unique fixed point. We also prove that on almost meshed-continua (a class of continua containing topological graphs and dendrites with closed or countable set of endpoints), periodic points are dense if and only if they are dense for the map induced on the hyperspace of all nonempty compact subsets.

math.DS↗
arXiv2013

Wijsman hyperspaces of non-separable metric spaces

Given a metric space $\langle X,ρ\rangle$, consider its hyperspace of closed sets $CL(X)$ with the Wijsman topology $τ_{W(ρ)}$. It is known that $\langle{CL(X),τ_{W(ρ)}}\rangle$ is metrizable if and only if $X$ is separable and it is an open question by Di Maio and Meccariello whether this is equivalent to $\langle{CL(X),τ_{W(ρ)}}\rangle$ being normal. In this paper we prove that if the weight of $X$ is a regular uncountable cardinal and $X$ is locally separable, then $\langle{CL(X),τ_{W(ρ)}}\rangle$ is not normal. We also solve some questions by Cao, Junnilla and Moors regarding isolated points in Wijsman hyperspaces.

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