Given a dendrite X and a continuous map f : X → X, we show the following are equivalent: (i) ω f is continuous and Per(f ) = n∈N f n (X); (ii) ω(x, f ) = Ω(x, f ) for each x ∈ X; and (iii) f is equicontinuous. Furthermore, we present some examples illustrating our results.2010 Mathematics Subject Classification. Primary: 54H20. Secondary: 37B45. 1
Definitions and preliminariesLet Z be a metric space, then given A ⊆ Z and ǫ > 0, the open ball about A of radius ǫ is denoted by V(A, ǫ). The interior, clousure, boundary and cardinality of A are denoted by A • , A, Bd(A) and |A|, respectively. A map is a continuous function. Given a compact metric space X, we denote by 2 X the set of all nonempty closed subsets of X, topologized by the Hausdorff metric which is defined as follows: for A, B ∈ 2 X , we setA continuum is a nonempty, compact, connected metric space. We say that a continuum X is a simple closed curve if X is homeomorphic to S 1 = {z ∈ C : |z| = 1}. A continuum X is a dendrite provided that X is locally connected and does not contain a simple closed curve. It is clear that dendrites are uniquely arcwise connected continua. So, if X is a dendrite and x, y ∈ X, we denote by [x, y] the unique arc joining x and y; also (x, y) will denote [x, y] \ {x, y}.Let X be a continuum. A point p ∈ X is called an end point of X provided that whenever U is open and p ∈ U, there exists an open set V ⊆ U such that x ∈ V and |Bd(V )| = 1. We denote by End(X) the collection of end points of X. Furthermore, p is a cut point of X, if X \ {p} is disconnected.