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André Caldas

Publications and source records attributed to André Caldas.

5 recordsLinked to original sources
arXiv2021

The Variational Principle for a $\mathbb{Z}_+^N$ Action on a Hausdorff Locally Compact Space

We extend the definition of topological pressure to locally compact Hausdorff spaces, and we demonstrate a "variational principle" comparing the topological and measure theoretic pressures. Given a continuous $\mathbb{Z}_+^N$-action $T$ over a locally compact Hausdorff space $X$ and a continuous function vanishing at infinity $f \in C_0(X)$, we define topological pressure $P(T,f)$ using open covers of a special type we call "admissible covers". With this topological pressure, we demonstrate that \begin{equation*} P(T,f) = \sup_μ P_μ(T,f), \end{equation*} where the supremum is taken over all $T$-invariant probability Radon measures over $X$, and is equal to $0$ when there is none. In the last section, we present an example that illustrates why admissible covers are so adequate to deal with the non-compact case, while some other approaches would fail.

math.DS↗
arXiv2016

Topological Pressure for Locally Compact Metrizable Systems

It is widely known that when $X$ is compact Hausdorff, and when $T: X \to X$ and $f: X \to \mathbb{R}$ are continuous, \begin{equation*} P(T,f) = \sup_{\text{$μ$: Radon probability}} \left( h_μ(T) + \int f\, \mathrm{d}μ\right), \end{equation*} where $P(T,f)$ is the "topological pressure" and $h_μ(T)$ is the measure theoretic entropy of $T$ with respect to $μ$. This result is known as "variational principle". We generalize the concept of "topological pressure" for the case where $X$ is a separable locally compact metric space. Our definitions are quite similar to those used in the compact case. Our main result is the validity of the "variational principle".

math.DS↗
arXiv2016

Entropy and Its Variational Principle for Locally Compact Metrizable Systems

For a given topological dynamical system $(X,T)$ over a compact set $X$ with a metric $d$, the "variational principle" states that \begin{equation*} \sup_μh_μ(T) = h(T) = h_d(T), \end{equation*} where $h_μ(T)$ is the Kolmogorov-Sinai entropy, with the supremum taken over every $T$-invariant probability measure, $h_d(T)$ is the Bowen entropy, and $h(T)$ is the topological entropy as defined by Adler, Konheim and McAndrew. In [9], the concept of topological entropy was adapted for the case where $T$ is a proper map and $X$ is locally compact separable and metrizable, and the variational principle was extended to \begin{equation*} \sup_μh_μ(T) = h(T) = \min_d h_d(T), \end{equation*} where the minimum is taken over every distance compatible with the topology of $X$. In the present work, we dropped the properness assumption, extending the above result for any continuous map $T$. We also apply our results to extend some previous formulas for the topological entropy of continuous endomorphisms of connected Lie groups proved in [4]. In particular, we prove that any linear transformation $T: V \to V$ over a finite dimensional vector space $V$ has null topological entropy.

math.DS↗
arXiv2012

Entropy of Endomorphisms of Lie Groups

We show, when $G$ is a nilpotent or reductive Lie group, that the entropy of any surjective endomorphism coincides with the entropy of its restriction to the toral component of the center of $G$. In particular, if $G$ is a semi-simple Lie group, the entropy of any surjective endomorphism always vanishes. Since every compact group is reductive, the formula for the entropy of a endomorphism of a compact group reduces to the formula for the entropy of an endomorphism of a torus.

math.DS↗