On the sum of two Borel sets. (English) Zbl 0192.40304
It is shown that the linear sum of two Borel subsets of the real line need not be Borel, even if one of them is compact and the other is \(G_\delta\). This result is extended to a fairly wide class of connected topological groups.
MSC:
03E15 | Descriptive set theory |
28A05 | Classes of sets (Borel fields, \(\sigma\)-rings, etc.), measurable sets, Suslin sets, analytic sets |