A note on tameness of families having bounded variation

作者：Megrelishvili Michael^*

来源：Topology and Its Applications, 2017, 217: 20-30.

DOI：10.1016/j.topol.2016.12.006

• Bounded variation
• Independent family
• Fragmented function
• Helly's selection theorem
• Linear order
• LOTS
• Order-compactification
• Sequential compactness

We show that for arbitrary linearly ordered set (X, <=) any bounded family of (not necessarily, continuous) real valued functions on X with bounded total variation does not contain independent sequences. We obtain generalized Belly's sequential compactness type theorems. One of the theorems asserts that for every compact metric space (Y, d) the compact space BVr(X, Y) of all functions X -> Y with variation <= r is sequentially compact in the pointwise topology. Another Belly type theorem shows that the compact space M+(X,Y) of all order preserving maps X -> Y is sequentially compact where Y is a compact metrizable partially ordered space in the sense of Nachbin.

• 出版日期2017-2-15