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Discovering the compactness properties in generalized-type metric spaces opens up a fascinating area of research. The present study tries to develop a theoretical framework for compactness with key properties in the recently developed interval metric space. This work begins with explaining the covers and open covers to define compact interval metric spaces and their main features. Next, a similar definition of compactness using the finite intersection property is introduced. Then, the famous Heine–Borel theorem for compactness is extended in the case of interval metric spaces. Also, the concepts of sequential-type compactness and Bolzano–Weierstrass (BW)-type compactness for interval metric spaces are introduced with their equivalency relationship. Finally, the notion of total boundedness in interval metric spaces and its connection with compactness is introduced, providing new insights into these mathematical concepts.

Let $\\def \\xmlpi #1{}\\def \\mathsfbi #1{\\boldsymbol {\\mathsf {#1}}}\\let \\le =\\leqslant \\let \\leq =\\leqslant \\let \\ge =\\geqslant \\let \\geq =\\geqslant \\def \\Pr {\\mathit {Pr}}\\def \\Fr {\\mathit {Fr}}\\def \\Rey {\\mathit {Re}}\\langle X,d \\rangle $ be a metric space. We characterise the family of subsets of $X$ on which each locally Lipschitz function defined on $X$ is bounded, as well as the family of subsets on which each member of two different subfamilies consisting of uniformly locally Lipschitz functions is bounded. It suffices in each case to consider real-valued functions.

In this paper, a new definition of fuzzy bounded sets and totally fuzzy bounded sets is introduced and properties of such sets are studied. Then a relation between totally fuzzy bounded sets and N-compactness is discussed. Finally, a geometric characterization for fuzzy totally bounded sets in I- topological vector spaces is derived.

If G is a locally compact Abelian group, let G+{{\\mathbf {G}}^ + } denote the underlying group of G equipped with the weakest topology that makes all the continuous characters of G continuous. Thus defined, G+{{\\mathbf {G}}^ + } is a totally bounded topological group. We prove: Theorem. G+{{\\mathbf {G}}^ + } is normal if and only if G is σ\\sigma-compact. When G is discrete, this theorem answers in the negative a question posed in 1990 by E. van Douwen, and it partially solves a problem posed in 1945 by A. Markov.