Abstract
An extended metric on a set X is a distance function that satisfies the usual properties of a metric except that it can assume values of infinity, in addition to nonnegative real values. Given a metrizable space we exhibit a universal space for all extended metric spaces compatible with the topology. Defining a set in an extended metric space to be bounded if it is contained in a finite union of open balls, we characterize those bornologies on X that can be realized as bornologies of metrically bounded sets. We also consider a second possible definition of bounded set in this setting.
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Dedicated to Petar Kenderov on his 70th birthday.
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Beer, G. The Structure of Extended Real-valued Metric Spaces. Set-Valued Var. Anal 21, 591–602 (2013). https://doi.org/10.1007/s11228-013-0255-2
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DOI: https://doi.org/10.1007/s11228-013-0255-2
Keywords
- Metric
- Extended real-valued metric
- Bounded set
- Partial function
- Bornology
- Metric bornology
- Isometry
- Free union topology
- Hu’s Theorem