Lower Semicontinuous Functions
نویسنده
چکیده
We define the notions of lower and upper semicontinuity for functions from a metric space to the extended real line. We prove that a function is both lower and upper semicontinuous if and only if it is continuous. We also give several equivalent characterizations of lower semicontinuity. In particular, we prove that a function is lower semicontinuous if and only if its epigraph is a closed set. Also, we introduce the notion of the lower semicontinuous hull of an arbitrary function and prove its basic properties.
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ورودعنوان ژورنال:
- Archive of Formal Proofs
دوره 2011 شماره
صفحات -
تاریخ انتشار 2011