Functions that preserve certain classes of sequences and locally Lipschitz functions

Abstract

The class of cofinally complete metric spaces lies between the class of complete metric spaces and that of compact metric spaces. It is known that a metric space (X, d) is cofinally complete if and only if every real-valued continuous function on (X, d) is cofinally Cauchy regular, where a function is said to be cofinally Cauchy regular or CC-regular for short if it preserves cofinally Cauchy sequences. Recently in 2017, Keremedis has defined almost bounded functions and AUC spaces [22]. We show that an AUC space is nothing but a cofinally complete metric space and an almost bounded function is nothing but a CC-regular function. Also in this paper, we study boundedness of various Lipschitz-type functions which are CC-regular as well and find equivalent characterizations of metric spaces on which such functions are uniformly continuous. Finally we explore some properties of cofinally Bourbaki-Cauchy regular functions, where a function is said to be cofinally Bourbaki-Cauchy regular if it preserves cofinally Bourbaki-Cauchy sequences [17] and find their relation with CC-regular functions.

Functions that preserve totally bounded sets vis-á-vis stronger notions of continuity

“…Using the above remark, we can prove the following result in a manner similar to the proof of Theorem 3.12 in [13].…”

“…Other than the above mentioned classes of continuous functions, we also study some relations of TB-regular functions with some Lipschitz-type functions. Much analysis on these functions and their applications can be found in [4,5,6,7,12,13]. Let us note their precise definitions in order of increasing size.…”